BACKPORT: xfrm/compat: Add 32=>64-bit messages translator

Provide the user-to-kernel translator under XFRM_USER_COMPAT, that
creates for 32-bit xfrm-user message a 64-bit translation.
The translation is afterwards reused by xfrm_user code just as if
userspace had sent 64-bit message.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
(cherry picked from commit 5106f4a8acff480e244300bc5097c0ad7048c3a2)
[adelva: nlmsg_parse_deprecated -> nlmsg_parse]
Bug: 163141236
Signed-off-by: Alistair Delva <adelva@google.com>
Change-Id: If15999b86e4704b75307fbcc3d7f0c8d8bc89e7a