move gsm_04_08_gprs.h to libosmocore

This requres the corresponding commit in libosmocore.
diff --git a/openbsc/src/gprs/gprs_gb_parse.c b/openbsc/src/gprs/gprs_gb_parse.c
index 63ac902..5ec3cf6 100644
--- a/openbsc/src/gprs/gprs_gb_parse.c
+++ b/openbsc/src/gprs/gprs_gb_parse.c
@@ -19,12 +19,12 @@
  */
 
 #include <osmocom/gsm/gsm48.h>
+#include <osmocom/gsm/protocol/gsm_04_08_gprs.h>
 
 #include <openbsc/gprs_gb_parse.h>
 
 #include <openbsc/gprs_utils.h>
 
-#include <openbsc/gsm_04_08_gprs.h>
 #include <openbsc/debug.h>
 
 #include <osmocom/gprs/gprs_bssgp.h>