irq_work: Introduce arch_irq_work_has_interrupt()

The nohz full code needs irq work to trigger its own interrupt so that
the subsystem can work even when the tick is stopped.

Lets introduce arch_irq_work_has_interrupt() that archs can override to
tell about their support for this ability.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

arch/um/include/asm/Kbuild

@@ -14,6 +14,7 @@ generic-y += hash.h
 generic-y += hw_irq.h
 generic-y += io.h
 generic-y += irq_regs.h
+generic-y += irq_work.h
 generic-y += kdebug.h
 generic-y += mcs_spinlock.h
 generic-y += mutex.h