libosmogb.pc.in: Fix missing dependency on libosmogsm

Change-Id: I5efa04d1c5cabc65b42de624b26fdbf9ebe746b1
diff --git a/libosmogb.pc.in b/libosmogb.pc.in
index 0a62426..5573bd9 100644
--- a/libosmogb.pc.in
+++ b/libosmogb.pc.in
@@ -6,6 +6,6 @@
 Name: Osmocom GPRS Gb Library
 Description: Osmocom GPRS Gb Interface (NS/BSSGP) Library
 Version: @VERSION@
-Requires: talloc, libosmocore, libosmovty
+Requires: talloc, libosmocore, libosmovty, libosmogsm
 Libs: -L${libdir} -losmogb
 Cflags: -I${includedir}/ -fno-strict-aliasing