sched/idle: Add missing checks to the exit condition of cpu_idle_poll()

cpu_idle_poll() is entered into when either the cpu_idle_force_poll is set or
tick_check_broadcast_expired() returns true. The exit condition from
cpu_idle_poll() is tif_need_resched().

However this does not take into account scenarios where cpu_idle_force_poll
changes or tick_check_broadcast_expired() returns false, without setting
the resched flag. So a cpu will be caught in cpu_idle_poll() needlessly,
thereby wasting power. Add an explicit check on cpu_idle_force_poll and
tick_check_broadcast_expired() to the exit condition of cpu_idle_poll()
to avoid this.

Change-Id: I9e48347dba41ee9980afa00e0fe5be0fdddb5e6e
Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20150121105655.15279.59626.stgit@preeti.in.ibm.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>
Git-commit: ff6f2d29bd31cdfa1ac494a8b26d2af8ba887d59
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Srinivasarao P <spathi@codeaurora.org>