Update CamHelper::exposureLines() and CamHelper::exposure() to take a line length duration parameter for use in the exposure calculations. For now, only use the minimum line length for all the calculations to match the existing IPA behavior. Signed-off-by: Naushir Patuck <naush@raspberrypi.com> Tested-by: Dave Stevenson <dave.stevenson@raspberrypi.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>