smp: Introduce a helper function to check for pending IPIs

smp: Introduce a helper function to check for pending IPIs

When governors used during cpuidle try to find the most optimal idle state
for a CPU or a group of CPUs, they are known to quite often fail. One
reason for this is, that they are not taking into account whether there has
been an IPI scheduled for any of the CPUs that are affected by the selected
idle state.

To enable pending IPIs to be taken into account for cpuidle decisions,
introduce a new helper function, cpus_peek_for_pending_ipi().

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>