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/tests/smpp/Makefile.am b/openbsc/tests/smpp/Makefile.am
index 9ab15c5..aab4de9 100644
--- a/openbsc/tests/smpp/Makefile.am
+++ b/openbsc/tests/smpp/Makefile.am
@@ -10,4 +10,4 @@
 	$(top_builddir)/src/libmsc/smpp_utils.c
 smpp_test_LDADD = \
 	$(top_builddir)/src/libcommon/libcommon.a \
-	$(LIBOSMOCORE_LIBS)
+	$(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS)