debian: .install: split mgcp-client out of legacy-mgcp

Change-Id: I681e9a1299607ff3a30de34c043da499c471bc31
diff --git a/debian/libosmo-mgcp-client-dev.install b/debian/libosmo-mgcp-client-dev.install
new file mode 100644
index 0000000..c12a86a
--- /dev/null
+++ b/debian/libosmo-mgcp-client-dev.install
@@ -0,0 +1,4 @@
+usr/include/osmocom/mgcp_client
+usr/lib/*/libosmo-mgcp-client.so
+usr/lib/*/libosmo-mgcp-client.a
+usr/lib/*/pkgconfig/libosmo-mgcp-client.pc