[XFRM] xfrm_user: Fix unaligned accesses.

Use memcpy() to move xfrm_address_t objects in and out
of netlink messages.  The vast majority of xfrm_user was
doing this properly, except for copy_from_user_state()
and copy_to_user_state().

Signed-off-by: David S. Miller <davem@davemloft.net>