xtensa: no need to reset handler if SA_ONESHOT

get_signal_to_deliver() already resets the signal handler if SA_ONESHOT
is set in ka->sa.sa_flags, there's no need to do it again in
handle_signal().

Furthermore, because we were modifying ka->sa.sa_handler (which is a
copy of sighand->action[]) instead of sighand->action[] the original
code actually had no effect on signal delivery.

Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>