ipa: Fix ipa_ccm_id_resp_parse on big endian systems

Change-Id: Iedc46ab53a4f76bbd98741c065fad3d9042a34a4
diff --git a/src/gsm/ipa.c b/src/gsm/ipa.c
index 8e64a1e..1563d0a 100644
--- a/src/gsm/ipa.c
+++ b/src/gsm/ipa.c
@@ -204,8 +204,8 @@
 
 	while (len >= 3) {
 		len -= 3;
-		t_len = *cur++ << 8;
-		t_len += *cur++;
+		t_len = osmo_load16be(cur);
+		cur += 2;
 		t_tag = *cur++;
 
 		if (t_len > len + 1) {