lms: init band
lms: init band

Gain setting without a band was apparently led to a very low output
level, thanks to defog for pointing this out.

Change-Id: I8b59d38dd7b0781776c9e61226185879541fdc53
Related: OS#3342

osmocom/osmo-trx,osmocom/osmo-trx,osmocom/osmo-trx,osmocom/osmo-trx