tiny signalfd cleanup

This is probably a leftover from a time when the return wasn't there yet.
Now the extra assignment is just irritating.

Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>