drivers: lora: sx1276: fix RFO TX power configuration
drivers: lora: sx1276: fix RFO TX power configuration

The PA_CONFIG register is currently not setup correctly for the RFO
path. The biggest problem is that the output power is incorrectly set
1dBm higher than requested. Additionally, the lower power levels are
not configured properly since the max power field in PA_CONFIG is
always configured for an output power between 0 and 15dBm.

To support lower than 0dBm, adjust the max power field in the
PA_CONFIG register to shift the output power range to -4--11 dBm when
the requested power is 0 or lower.

Signed-off-by: Andreas Sandberg <b15c342f1de186996bcca5e1a23cd684d2fadb32@sandberg.pp.se>
[Marcin: rebase on master]
Signed-off-by: Marcin Niestroj <63506c06cfbc47ace147db1702f6e751f5ac2132@grinn-global.com>

finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr