Input: ambakmi - request a shared interrupt for AMBA KMI devices

Recent ARM boards have the KMI devices share one interrupt line rather
than having dedicated IRQs. Update the driver to take that into account.

Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>