Switch from polling to interrupt mode.

Successfully tested on a S905GXBB-based Odroid C2.
Signed-off-by: NHeiner Kallweit <hkallweit1@gmail.com>
Acked-by: NMartin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: NMartin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>