ieee802154: add TX power control to wpan_phy

Replace the current u8 transmit_power in wpan_phy with s8 transmit_power.
The u8 field contained the actual tx power and a tolerance field,
which no physical radio every used. Adjust sysfs entries to keep
compatibility with userspace, give tolerances of +-1dB statically there.

This patch only adds support for this in the at86rf230 driver and the
RF212 chip. Configuration calculation for RF212 is also somewhat basic,
but does the job - the RF212 datasheet gives a large table with
suggested values for combinations of TX power and page/channel, if this
does not work well, we might have to copy the whole table.

Signed-off-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/nl802154.h

@@ -70,6 +70,8 @@ enum {
 	IEEE802154_ATTR_PHY_NAME,
 	IEEE802154_ATTR_DEV_TYPE,
 
+	IEEE802154_ATTR_TXPOWER,
+
 	__IEEE802154_ATTR_MAX,
 };
 
@@ -122,6 +124,8 @@ enum {
 	IEEE802154_ADD_IFACE,
 	IEEE802154_DEL_IFACE,
 
+	IEEE802154_SET_PHYPARAMS,
+
 	__IEEE802154_CMD_MAX,
 };