modetest: Pass format_info to fill_tiles functions

The fourcc is inside the format_info structure, so if we want to use
it inside the various fill_tiles functions, we need to pass down the
whole format_info, not just the rgb/yuv infos.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>