Revert "xfrm: For 32/64 compatability wrt. xfrm_usersa_info"

This reverts commit fc8c7dc1

.

As indicated by Jiri Klimes, this won't work.  These numbers are
not only used the size validation, they are also used to locate
attributes sitting after the message.

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