Transceiver: Store TRXD version per channel

The setting is negotiatied by osmo-bts-trx on each channel, so let's
keep and use state per channel instead of overwriting the state from
different channels.
Take the chance to change related log lines to also print the channel
number.

Change-Id: If9cf95e89d38d0155ab48b8c0977ca5f381c2aad
2 files changed