sgsn: gtp: Drop related pdp contexts on echo timeout against GGSN

Change-Id: I7e97bac1c13a2c26203eb64e590fd75d77eb44bd
diff --git a/src/gprs/gprs_sgsn.c b/src/gprs/gprs_sgsn.c
index 7174bd5..829204e 100644
--- a/src/gprs/gprs_sgsn.c
+++ b/src/gprs/gprs_sgsn.c
@@ -759,6 +759,11 @@
 	return num;
 }
 
+int sgsn_ggsn_ctx_drop_all_pdp(struct sgsn_ggsn_ctx *ggsn)
+{
+	return sgsn_ggsn_ctx_drop_all_pdp_except(ggsn, NULL);
+}
+
 void sgsn_ggsn_ctx_add_pdp(struct sgsn_ggsn_ctx *ggc, struct sgsn_pdp_ctx *pdp)
 {
 	llist_add(&pdp->ggsn_list, &ggc->pdp_list);