powerpc/powernv: Fix endian issues with OPAL async code

OPAL defines opal_msg as a big endian struct so we have to
byte swap it on little endian builds.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 7835d5b..778a279 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -281,6 +281,7 @@
 	 * value in /proc/device-tree.
 	 */
 	static struct opal_msg msg;
+	u32 type;
 
 	ret = opal_get_msg(__pa(&msg), sizeof(msg));
 	/* No opal message pending. */
@@ -294,13 +295,14 @@
 		return;
 	}
 
+	type = be32_to_cpu(msg.msg_type);
+
 	/* Sanity check */
-	if (msg.msg_type > OPAL_MSG_TYPE_MAX) {
-		pr_warning("%s: Unknown message type: %u\n",
-				__func__, msg.msg_type);
+	if (type > OPAL_MSG_TYPE_MAX) {
+		pr_warning("%s: Unknown message type: %u\n", __func__, type);
 		return;
 	}
-	opal_message_do_notify(msg.msg_type, (void *)&msg);
+	opal_message_do_notify(type, (void *)&msg);
 }
 
 static int opal_message_notify(struct notifier_block *nb,