usb: gadget: move gadget API functions to udc-core

instead of defining all functions as static inlines,
let's move them to udc-core and export them with
EXPORT_SYMBOL_GPL, that way we can make sure that
only GPL drivers will use them.

As a side effect, it'll be nicer to add tracepoints
to the gadget API.

While at that, also fix Kconfig dependencies to
avoid randconfig build failures.

Acked-By: Sebastian Reichel <sre@kernel.org>
Acked-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/phy/Kconfig

@@ -176,6 +176,7 @@ config TWL4030_USB
 	tristate "TWL4030 USB Transceiver Driver"
 	depends on TWL4030_CORE && REGULATOR_TWL4030 && USB_MUSB_OMAP2PLUS
 	depends on USB_SUPPORT
+	depends on USB_GADGET || !USB_GADGET # if USB_GADGET=m, this can't 'y'
 	select GENERIC_PHY
 	select USB_PHY
 	help

drivers/power/Kconfig

@@ -309,6 +309,7 @@ config BATTERY_RX51
 config CHARGER_ISP1704
 	tristate "ISP1704 USB Charger Detection"
 	depends on USB_PHY
+	depends on USB_GADGET || !USB_GADGET # if USB_GADGET=m, this can't be 'y'
 	help
 	  Say Y to enable support for USB Charger Detection with
 	  ISP1707/ISP1704 USB transceivers.

drivers/usb/host/Kconfig

@@ -180,7 +180,7 @@ config USB_EHCI_MXC
 config USB_EHCI_HCD_OMAP
 	tristate "EHCI support for OMAP3 and later chips"
 	depends on ARCH_OMAP
-	select NOP_USB_XCEIV
+	depends on NOP_USB_XCEIV
 	default y
 	---help---
 	  Enables support for the on-chip EHCI controller on

drivers/usb/phy/Kconfig

@@ -21,6 +21,7 @@ config AB8500_USB
 config FSL_USB2_OTG
 	bool "Freescale USB OTG Transceiver Driver"
 	depends on USB_EHCI_FSL && USB_FSL_USB2 && USB_OTG_FSM && PM
+	depends on USB_GADGET || !USB_GADGET # if USB_GADGET=m, this can't be 'y'
 	select USB_PHY
 	help
 	  Enable this to support Freescale USB OTG transceiver.
@@ -29,6 +30,7 @@ config ISP1301_OMAP
 	tristate "Philips ISP1301 with OMAP OTG"
 	depends on I2C && ARCH_OMAP_OTG
 	depends on USB
+	depends on USB_GADGET || !USB_GADGET # if USB_GADGET=m, this can't be 'y'
 	select USB_PHY
 	help
 	  If you say yes here you get support for the Philips ISP1301
@@ -43,7 +45,7 @@ config ISP1301_OMAP
 config KEYSTONE_USB_PHY
 	tristate "Keystone USB PHY Driver"
 	depends on ARCH_KEYSTONE || COMPILE_TEST
-	select NOP_USB_XCEIV
+	depends on NOP_USB_XCEIV
 	help
 	  Enable this to support Keystone USB phy. This driver provides
 	  interface to interact with USB 2.0 and USB 3.0 PHY that is part
@@ -51,6 +53,7 @@ config KEYSTONE_USB_PHY
 
 config NOP_USB_XCEIV
 	tristate "NOP USB Transceiver Driver"
+	depends on USB_GADGET || !USB_GADGET # if USB_GADGET=m, NOP can't be built-in
 	select USB_PHY
 	help
 	  This driver is to be used by all the usb transceiver which are either
@@ -63,9 +66,9 @@ config AM335X_CONTROL_USB
 config AM335X_PHY_USB
 	tristate "AM335x USB PHY Driver"
 	depends on ARM || COMPILE_TEST
+	depends on NOP_USB_XCEIV
 	select USB_PHY
 	select AM335X_CONTROL_USB
-	select NOP_USB_XCEIV
 	select USB_COMMON
 	help
 	  This driver provides PHY support for that phy which part for the
@@ -92,6 +95,7 @@ config TWL6030_USB
 config USB_GPIO_VBUS
 	tristate "GPIO based peripheral-only VBUS sensing 'transceiver'"
 	depends on GPIOLIB || COMPILE_TEST
+	depends on USB_GADGET || !USB_GADGET # if USB_GADGET=m, this can't be 'y'
 	select USB_PHY
 	help
 	  Provides simple GPIO VBUS sensing for controllers with an
@@ -112,6 +116,7 @@ config OMAP_OTG
 config TAHVO_USB
 	tristate "Tahvo USB transceiver driver"
 	depends on MFD_RETU && EXTCON
+	depends on USB_GADGET || !USB_GADGET # if USB_GADGET=m, this can't be 'y'
 	select USB_PHY
 	help
 	  Enable this to support USB transceiver on Tahvo. This is used
@@ -140,6 +145,7 @@ config USB_ISP1301
 config USB_MSM_OTG
 	tristate "Qualcomm on-chip USB OTG controller support"
 	depends on (USB || USB_GADGET) && (ARCH_QCOM || COMPILE_TEST)
+	depends on USB_GADGET || !USB_GADGET # if USB_GADGET=m, this can't be 'y'
 	depends on RESET_CONTROLLER
 	depends on EXTCON
 	select USB_PHY
@@ -169,6 +175,7 @@ config USB_QCOM_8X16_PHY
 config USB_MV_OTG
 	tristate "Marvell USB OTG support"
 	depends on USB_EHCI_MV && USB_MV_UDC && PM && USB_OTG
+	depends on USB_GADGET || !USB_GADGET # if USB_GADGET=m, this can't be 'y'
 	select USB_PHY
 	help
 	  Say Y here if you want to build Marvell USB OTG transciever