media: vsp1: Add support for missing 16-bit RGB555 formats

Add support for the V4L2_PIX_FMT_RGBA555, V4L2_PIX_FMT_RGBX555,
V4L2_PIX_FMT_ABGR555, V4L2_PIX_FMT_XBGR555, V4L2_PIX_FMT_BGRA555 and
V4L2_PIX_FMT_BGRX555 formats to the VSP driver.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>