osmo-trx: set up signals using libosmocore helpers
osmo-trx: set up signals using libosmocore helpers

Change-Id: I86e78cd6054d0deff1b1aa061299d9f307e2a352

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