aio: simplify read_events()

Change wait_event_hrtimeout() to not call __wait_event_hrtimeout() if
timeout == 0, this matches other _timeout() helpers in wait.h.

This allows to simplify its only user, read_events(), it no longer needs
to optimize the "until == 0" case by hand.

Note: this patch doesn't use ___wait_cond_timeout because _hrtimeout()
also differs in that it returns 0 if succeeds and -ETIME on timeout.
Perhaps we should change this to make it fully compatible with other
helpers.

Link: http://lkml.kernel.org/r/20190607175413.GA29187@redhat.com


Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Eric Wong <e@80x24.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>