drm/hypervdrm: Use vblank timer

drm/hypervdrm: Use vblank timer

HyperV's virtual hardware does not provide vblank interrupts. Use a
vblank timer to simulate the interrupt. Rate-limits the display's
update frequency to the display-mode settings. Avoids excessive CPU
overhead with compositors that do not rate-limit their output.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250916083816.30275-5-tzimmermann@suse.de