Add support for the virtual irq since now MFD only handles virtual irq
Without this patch rtc device will fail in registration.

(akpm: Ashish has a different version whcih will be needed for 3.8.x and
earlier kernels)
Signed-off-by: Ashish <ashish.jangam@kpitcummins.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>