drm: Guard DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE

drm: Guard DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE

The client cap is currently advertised unconditionally, even for drivers
that do not support plane color pipelines. If clients supporting the latter,
like Wayland compositors or tools like drm_info, enable the client cap on
such drivers they will be left without both color pipeline and the legacy
properties COLOR_ENCODING and COLOR_RANGE, effectively breaking YUV->RGB
conversion support.

Prevent that by only marking the cap supported if there are actually planes
with color pipelines.

Note: while the color pipeline replacement for the legacy properties is
still under review (1), we can assume that it will work as a drop-in
replacement. That means any plane on any hardware currently supporting
the legacy properties will be able to offer a functionally equal color
pipeline and there will be no technical reason keep using the legacy
properties if both the driver and the client support the new API.

[1] https://lore.kernel.org/dri-devel/20260623164812.81110-1-harry.wentland@amd.com/

Signed-off-by: Robert Mader <robert.mader@collabora.com>
Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Fixes: 179ab8e7d7b3 ("drm/colorop: Introduce DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE")
Link: https://patch.msgid.link/20260703073230.19982-1-robert.mader@collabora.com
Suggested-by: Maarten Lankhorst <dev@lankhorst.se>
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>