media: bcm2835-isp: fix bytes per line calculations for some image formats

The bytes per line numbers calculated by get_bytesperline was not
matching the equivalent calculation being performed by the VideoCore
(mostly by the calculate_pitch function there), resulting in failures
to set the image format with some image width values. This patches up
the RGB24 and YUYV type formats to match the VideoCore calculation.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>