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>