rm dup: use channel type names from libosmocore

In gsm_lchant_name(enum gsm_chan_t), use the gsm_chan_t_names value strings
from libosmocore instead of redefining the same strings. The list from
libosmocore is also more complete, including CCCH and PDTCH.

Add a todo comment to move to libosmocore.

In consequence, libosmogsm linkage needs to be added to osmo-bsc_mgcp,
mgcp_test, mgcp_transcoding_test and smpp_mirror, smpp_test.

Change-Id: If65ee7c0619cbc0acb0a15045bd5a969442c93cc
diff --git a/openbsc/src/osmo-bsc_mgcp/Makefile.am b/openbsc/src/osmo-bsc_mgcp/Makefile.am
index 949cb64..a48f24b 100644
--- a/openbsc/src/osmo-bsc_mgcp/Makefile.am
+++ b/openbsc/src/osmo-bsc_mgcp/Makefile.am
@@ -9,6 +9,6 @@
 
 osmo_bsc_mgcp_LDADD = $(top_builddir)/src/libcommon/libcommon.a \
 		 $(top_builddir)/src/libmgcp/libmgcp.a -lrt \
-		 $(LIBOSMOVTY_LIBS) $(LIBOSMOCORE_LIBS) \
+		 $(LIBOSMOVTY_LIBS) $(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS) \
 		 $(LIBOSMONETIF_LIBS) $(LIBBCG729_LIBS) \
 		 $(LIBRARY_GSM)