PM / Sleep: Do not check wakeup too often in try_to_freeze_tasks()

Use the observation that it is more efficient to check the wakeup
variable once before the loop reporting tasks that were not
frozen in try_to_freeze_tasks() than to do that in every step of that
loop.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

Conflicts:

	kernel/power/process.c

Signed-off-by: Srivalli Oguri <oguri@codeaurora.org>
(cherry picked from commit a15cc22b56b803b8f943c57d9535bdb9953ff3ec)

Change-Id: Ic41cd71a0ec49cd0c633c14aa3fce02025a4de3f
Signed-off-by: Sridhar Gujje <sgujje@codeaurora.org>