eventpoll: no need to mask the result of epi_item_poll() again

two callers that do so don't need to bother - we'd already
masked it with epi->event.events, which
	* couldn't have changed since we are holding ->mtx
	* had been set to event->events
	* is still equal to event->events, since *event is never
changed by anything.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>