VBLANK callbacks in struct drm_driver are deprecated in favor of
their equivalents in struct drm_crtc_funcs. Convert vmwgfx over.

v2:
	* remove accidental whitespace fixes
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Thomas Hellstrom <thellstrom@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200123135943.24140-21-tzimmermann@suse.de