[XFRM]: Rearrange struct xfrm_aevent_id for better compatibility.

struct xfrm_aevent_id needs to be 32-bit + 64-bit align friendly.

Based upon suggestions from Yoshifuji.
Signed-off-by: NJamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/xfrm.h

@@ -259,8 +259,8 @@ struct xfrm_usersa_id {
 };
 
 struct xfrm_aevent_id {
-	__u32				flags;
 	struct xfrm_usersa_id		sa_id;
+	__u32				flags;
 };
 
 struct xfrm_userspi_info {