drm/vkms: Remove usage of legacy drm_crtc members

drm/vkms: Remove usage of legacy drm_crtc members

Some members of the drm_crtc structure have been deprecated in favor of
equivalent members in the drm_crtc_state structure. As reported by Ville
Syrjala [1], the VKMS driver was still using these deprecated fields. This
commit updates the VKMS driver to use the new drm_crtc_state fields
instead.

Additionally, this commit removes the call to
`drm_calc_timestamping_constants` in `vkms_enable_vblank` as it is
redundant. This calculation is already performed in
`vkms_atomic_commit_tail` by calling
`drm_atomic_helper_commit_modeset_disables`.

[1]:https://lore.kernel.org/all/20241002182200.15363-1-ville.syrjala@linux.intel.com/

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241003-remove-legacy-v1-1-0b7db1f1a1a6@bootlin.com
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>