genirq: Create helper for flow handler entry check

All flow handlers - except the per cpu ones - check for an interrupt
in progress and an eventual concurrent polling on another cpu.

Create a helper function for the repeated code pattern.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>