Move gtphub header to include/osmocom/gtphub/

Change-Id: I82e1f2a3bc8e22b28747a540879bd661f1704cde
diff --git a/src/gtphub/gtphub_sock.c b/src/gtphub/gtphub_sock.c
index 1837533..59a0d42 100644
--- a/src/gtphub/gtphub_sock.c
+++ b/src/gtphub/gtphub_sock.c
@@ -25,7 +25,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <osmocom/sgsn/gtphub.h>
+#include <osmocom/gtphub/gtphub.h>
 #include <osmocom/sgsn/debug.h>
 
 /* Convenience makro, note: only within this C file. */