Wrong register number for RegPaDac in radio.c

[cyberman54]

wrong RegPaDAC register number in radio.c
RegPaDac has register number 0x4D, not 0x5A, referencing to Semtech SX1276 datasheet.

[terrillmoore]

Agreed, this is wrong. Apparently innocuous because the default setting is the same as the value that's always written. I'll do a pull request. Thanks!