Add YUV8_1X24 media bus format

This patch adds the media bus format for a 24-bit bus format with three
8-bit YUV components.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>