cpuidle: Add need_resched() check

The cpuidle framework is disabled as part of suspend. In this scenario,
the cpu may enter wfi without checking the need_resched() flag.
Prevent this from occuring.

CRs-fixed: 920501
Change-Id: Ib2077833279d84b2aea25c61198dfbdcf4566ea4
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>