libosmo-pfcp.pc.in: add missing libosmogsm

We use osmo_apn_from_str() and osmo_apn_to_str(), defined in libosmogsm,
since this commit:
"fix coding of Network Instance IE"
8368e7d5d59140fc77b890493a47a08cd644e2f8
I9d67464ef0f92b0512cfd6e48d203f8828a82a19

Since libosmo-pfcp merely calls the two functions and none of
libosmogsm is exposed in the libosmo-pfcp API, it suffices to use
Requires.private in the .pc file.

Change-Id: Ie1c92d251af6a3e42759ff0da0d3693356b5e1d3
---
M libosmo-pfcp.pc.in
1 file changed, 20 insertions(+), 0 deletions(-)

diff --git a/libosmo-pfcp.pc.in b/libosmo-pfcp.pc.in
index 0ed5160..58a6164 100644
--- a/libosmo-pfcp.pc.in
+++ b/libosmo-pfcp.pc.in
@@ -7,5 +7,6 @@
 Description: C Utility Library that implements the PFCP protocol and endpoint
 Version: @VERSION@
 Requires: libosmo-gtlv, libosmocore, talloc
+Requires.private: libosmogsm
 Libs: -L${libdir} -losmo-pfcp
 Cflags: -I${includedir}/

