media: ov64a40: Report the full crop rectangle

The analogue crop rectangle defined in the sensor supported modes
reports the index of the last pixel in the horizontal/vertical
directions, instead of reporting the actual rectangle's width and
height.

Fix this by reporting the correct width and height and subtracting 1
pixel when applying the rectangle sizes to the sensor's registers.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>