fs/userfaultfd.c: drop dead code

Calculation of start end end in __wake_userfault function are not used
and can be removed.

Link: http://lkml.kernel.org/r/1494930917-3134-1-git-send-email-rppt@linux.vnet.ibm.com


Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>