media: renesas: vsp1: Fix media bus code setup on RWPF source pad

media: renesas: vsp1: Fix media bus code setup on RWPF source pad

The RWPF source pad media bus code can only be different from the sink
pad code when enabling color space conversion, which can only convert
between RGB and YUV. If the sink pad code is HSV, no conversion is
possible. Fix the pad set format handler to reflect this hardware
limitation.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
Link: https://lore.kernel.org/r/20250429232904.26413-5-laurent.pinchart+renesas@ideasonboard.com
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>