Update criu/include/linux/userfaultfd.h

This is the version from v4.11-rc5. Apparently, that would be the userfault
ABI for the next few month.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>