bts-trx: sched_lchan_tchf: Drop impossible code path
bts-trx: sched_lchan_tchf: Drop impossible code path

It cannot happen that msg1 is NULL and msg2 is not null, since they are
deuqueed from same place. Only possible combinations are:
msg1!=NULL && msg2!=NULL
msg1!=NULL && msg2==NULL

Change-Id: Ifd789844b1a7dfba596664de440d4c20b9f4c78f

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