openvswitch: Fix the type of struct ovs_key_nd nd_target field.

Should be the same as other IPv6 address fields.

Current master produces sparse warnings without this change.
Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>

include/uapi/linux/openvswitch.h

@@ -400,7 +400,7 @@ struct ovs_key_arp {
 };
 
 struct ovs_key_nd {
-	__u32 nd_target[4];
+	__be32	nd_target[4];
 	__u8	nd_sll[ETH_ALEN];
 	__u8	nd_tll[ETH_ALEN];
 };