drm/vkms: Switch to managed for crtc

The current VKMS driver uses managed function to create crtc, but
don't use it to properly clean the crtc workqueue. It is not an
issue yet, but in order to support multiple devices easily,
convert this code to use drm and device managed helpers.

Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250116-google-vkms-managed-v9-4-3e4ae1bd05a0@bootlin.com


Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>