drm/vkms: Allow to attach planes and CRTCs

drm/vkms: Allow to attach planes and CRTCs

Add a list of possible CRTCs to the plane configuration and helpers to
attach, detach and get the primary and cursor planes attached to a CRTC.

Now that the default configuration has its planes and CRTC correctly
attached, configure the output following the configuration.

Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Co-developed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250218101214.5790-11-jose.exposito89@gmail.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>