libosmo-mgcp-client: don't link against libosmonetif

This fixes the following dpkg-shlibdeps warning:

Change-Id: If60583b2bec344fc674af6f129787206540bc9fc
dpkg-shlibdeps: warning: package could avoid a useless dependency if debian/libosmo-mgcp-client0/usr/lib/x86_64-linux-gnu/libosmo-mgcp-client.so.0.0.0 was not linked against libosmonetif.so.4 (it uses none of the library's symbols)
diff --git a/src/libosmo-mgcp-client/Makefile.am b/src/libosmo-mgcp-client/Makefile.am
index b376cd9..de35f87 100644
--- a/src/libosmo-mgcp-client/Makefile.am
+++ b/src/libosmo-mgcp-client/Makefile.am
@@ -9,14 +9,12 @@
 	-Wall \
 	$(LIBOSMOCORE_CFLAGS) \
 	$(LIBOSMOVTY_CFLAGS) \
-	$(LIBOSMONETIF_CFLAGS) \
 	$(COVERAGE_CFLAGS) \
 	$(NULL)
 
 AM_LDFLAGS = \
 	$(LIBOSMOCORE_LIBS) \
 	$(LIBOSMOVTY_LIBS) \
-	$(LIBOSMONETIF_LIBS) \
 	$(COVERAGE_LDFLAGS) \
 	$(NULL)