driver: ieee802154: rf2xx: implement setting tx power

Implemented rf2xx_set_txpower() in ieee802154_rf2xx.c by mapping dBm
values to RF2XX register values.

Signed-off-by: Kari Severinkangas <kari.severinkangas@tridonic.com>
Signed-off-by: Markus Becker <markus.becker@tridonic.com>
1 file changed