sysmobts: Fix the initialization of the BTS manager code
sysmobts: Fix the initialization of the BTS manager code

The code should only run for the sysmoBTS 2050 and TRX 0.
If the device is not marked as 2050 the code would attempt
to open /dev/ttyS0 and block forever.

geosphere/osmo-bts,geosphere/osmo-bts,geosphere/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts,telenoobie/osmo-bts,telenoobie/osmo-bts,telenoobie/osmo-bts,telenoobie/osmo-bts,geosphere/osmo-bts