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

v4:
	* add argument names in function declaration
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200123135943.24140-10-tzimmermann@suse.de