media: v4l: Add definitions for missing 16-bit RGB555 formats

The V4L2 API is missing the 16-bit RGB555 formats for the RGBA, RGBX,
ABGR, XBGR, BGRA and BGRX component orders. Add them, using the same
4CCs as DRM.

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>