osmo-bts-trx: move MTS parser into trx_data_parse_mts()
osmo-bts-trx: move MTS parser into trx_data_parse_mts()

This would allow to re-use this code from the TRXDv2 parser.

Change-Id: I2de2cb2d58110452d8dedbcacfef28f85f6d67c1
Related: SYS#4895, OS#4941, OS#4006

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts