[media] smiapp: Add driver

Add driver for SMIA++/SMIA image sensors. The driver exposes the sensor as
three subdevs, pixel array, binner and scaler --- in case the device has a
scaler.

Currently it relies on the board code for external clock handling. There is
no fast way out of this dependency before the ISP drivers (omap3isp) among
others will be able to export that clock through the clock framework
instead.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>