Move struct gsm_bts_trx: gsm-data.* => bts_trx.*

See rant fro similar recent commit moving stuff to bts.*.

Change-Id: I11758ca3d255d849d77bd068f24bb68bde1f89a5
diff --git a/include/osmocom/bsc/Makefile.am b/include/osmocom/bsc/Makefile.am
index 4d2df20..c2a82ce 100644
--- a/include/osmocom/bsc/Makefile.am
+++ b/include/osmocom/bsc/Makefile.am
@@ -11,6 +11,7 @@
 	bsc_subscr_conn_fsm.h \
 	bss.h \
 	bts.h \
+	bts_trx.h \
 	bts_ipaccess_nanobts_omlattr.h \
 	chan_alloc.h \
 	codec_pref.h \