Drop gprs_msgb_resize_area with libosmocore replacement

gprs_msgb_resize_area was introduced in libosmocore 0.94
(f78ec5ce0d0f6038147d9b9e14d81094309ba5d5) as msgb_resize_area. Let's use
that one to avoid code duplication.

Change-Id: Ib80f7b2b186d87f21d63d9b0bec58175170c905c
diff --git a/src/gprs/gb_proxy_patch.c b/src/gprs/gb_proxy_patch.c
index 496f605..9cca9a8 100644
--- a/src/gprs/gb_proxy_patch.c
+++ b/src/gprs/gb_proxy_patch.c
@@ -112,7 +112,7 @@
 		     osmo_apn_to_str(str1, apn, apn_len));
 
 		*new_apn_ie_len = 0;
-		gprs_msgb_resize_area(msg, apn_ie, apn_ie_len, 0);
+		msgb_resize_area(msg, apn_ie, apn_ie_len, 0);
 	} else {
 		/* Resize the IE */
 		char str1[110];
@@ -129,7 +129,7 @@
 				       peer->cfg->core_apn_size));
 
 		*new_apn_ie_len = peer->cfg->core_apn_size + 2;
-		gprs_msgb_resize_area(msg, apn, apn_len, peer->cfg->core_apn_size);
+		msgb_resize_area(msg, apn, apn_len, peer->cfg->core_apn_size);
 		memcpy(apn, peer->cfg->core_apn, peer->cfg->core_apn_size);
 		hdr->apn_len = peer->cfg->core_apn_size;
 	}
@@ -463,4 +463,3 @@
 
 	return 1;
 }
-