pinctrl: Show selected function and group in pinmux-pins debugfs

Until recently, the pinctrl pinmux-pins debugfs file displayed the
selected function for each owned pin. This feature was removed during
restructing in support of recent API rework. This change restoreds this
feature, and also displays the group that the function was selected on,
in case a pin is a member of multiple groups.

Based on work by: Linus Walleij <linus.walleij@linaro.org>

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/core.h

@@ -126,6 +126,7 @@ struct pinctrl_setting {
  * @owner: The name of the entity owning the pin. Typically, this is the name
  *	of the device that called pinctrl_get(). Alternatively, it may be the
  *	name of the GPIO passed to pinctrl_request_gpio().
+ * @mux_setting: The most recent selected mux setting for this pin, if any.
  */
 struct pin_desc {
 	struct pinctrl_dev *pctldev;
@@ -135,6 +136,7 @@ struct pin_desc {
 #ifdef CONFIG_PINMUX
 	unsigned usecount;
 	const char *owner;
+	const struct pinctrl_setting_mux *mux_setting;
 #endif
 };