osmo-msc: Don't link against libasn1c

osmo-msc doesn't use any API/symbols of libasn1c directlry.  Rather,
we use libosmo-ranap which in turn uses libasn1c.  Let the linker
work out that dependency.

This fixes the following dpkg-shlibdeps warning:

Change-Id: I2f840884d8f1cc542de1e26acd3d4215bd2fd899
dpkg-shlibdeps: warning: package could avoid a useless dependency if debian/osmo-msc/usr/bin/osmo-msc was not linked against libasn1c.so.0 (it uses none of the library's symbols)
diff --git a/src/osmo-msc/Makefile.am b/src/osmo-msc/Makefile.am
index 85a5a5a..e296f97 100644
--- a/src/osmo-msc/Makefile.am
+++ b/src/osmo-msc/Makefile.am
@@ -51,6 +51,5 @@
 if BUILD_IU
 osmo_msc_LDADD += \
 	$(LIBOSMORANAP_LIBS) \
-	$(LIBASN1C_LIBS) \
 	$(NULL)
 endif
diff --git a/tests/msc_vlr/Makefile.am b/tests/msc_vlr/Makefile.am
index aa2b3fe..9af9870 100644
--- a/tests/msc_vlr/Makefile.am
+++ b/tests/msc_vlr/Makefile.am
@@ -43,7 +43,6 @@
 	$(LIBOSMOABIS_LIBS) \
 	$(LIBOSMOSIGTRAN_LIBS) \
 	$(LIBOSMORANAP_LIBS) \
-	$(LIBASN1C_LIBS) \
 	$(LIBOSMOMGCPCLIENT_LIBS) \
 	$(LIBRARY_GSM) \
 	-ldbi \
diff --git a/tests/sms_queue/Makefile.am b/tests/sms_queue/Makefile.am
index 1f8ee7b..a912be1 100644
--- a/tests/sms_queue/Makefile.am
+++ b/tests/sms_queue/Makefile.am
@@ -43,7 +43,6 @@
 	$(LIBOSMOABIS_LIBS) \
 	$(LIBOSMOSIGTRAN_LIBS) \
 	$(LIBOSMORANAP_LIBS) \
-	$(LIBASN1C_LIBS) \
 	$(LIBOSMOMGCPCLIENT_LIBS) \
 	$(LIBRARY_GSM) \
 	-ldbi \