genirq: Provide compat handling for chip->unmask()

Wrap the old chip function unmask() until the migration is complete
and the old chip functions are removed.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20100927121842.043608928@linutronix.de>
Reviewed-by: H. Peter Anvin <hpa@zytor.com>
Reviewed-by: Ingo Molnar <mingo@elte.hu>

kernel/irq/handle.c

@@ -360,7 +360,6 @@ struct irq_chip dummy_irq_chip = {
 	.enable		= compat_noop,
 	.disable	= compat_noop,
 	.ack		= compat_noop,
-	.unmask		= compat_noop,
 	.end		= compat_noop,
 };