BACKPORT: xfrm/compat: Translate 32-bit user_policy from sockptr

Provide compat_xfrm_userpolicy_info translation for xfrm setsocketopt().
Reallocate buffer and put the missing padding for 64-bit message.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
(cherry picked from commit 96392ee5a13b992563cfe07d23ee30d333b89126)
[adelva: Edited around removed compat check in Android kernels]
Bug: 163141236
Signed-off-by: Alistair Delva <adelva@google.com>
Change-Id: I32a6495cd92fa13c956fca88aa5d80716155b8ae