drm/vmwgfx: Convert to DRM vblank timers

drm/vmwgfx: Convert to DRM vblank timers

Replace vmwgfx's vblank timer with DRM's common implementation. The
timer handling is almost identical with a few additional bug fixes in
the common code.

Replace most of vmwgfx's vmw_vkms_get_vblank_timestamp() with the
shared helper drm_crtc_vblank_get_vblank_timeout(). The common helper
also works in the presence of delayed vblank timeouts that modify the
vblank counter concurrently.

Set the timeout handler to vmw_vkms_handle_vblank_timeout(). In addition
to handling vblank events, this function also controls CRC generation.

Remove all the hrtimer-related code from vmwgfx. DRM vblank timers
provides this.

v2:
- only cancel vblank timer in CRTC cleanup if vkms_enabled (Zack)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Zack Rusin <zack.rusin@broadcom.com>
Link: https://patch.msgid.link/20260427150250.699768-4-tzimmermann@suse.de