Move both versions, which are highly similar, to uaccess.h.
Note that, for x86_64, X86_WP_WORKS_OK is always defined.
Signed-off-by: NGlauber Costa <gcosta@redhat.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>