drm/vkms: Set preferred depth correctly

The only thing we support is xrgb8888.
Acked-by: NThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: NMelissa Wen <melissa.srw@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Cc: Melissa Wen <melissa.srw@gmail.com>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201009232156.3916879-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/vkms/vkms_drv.c

@@ -124,7 +124,7 @@ static int vkms_modeset_init(struct vkms_device *vkmsdev)
 	dev->mode_config.max_height = YRES_MAX;
 	dev->mode_config.cursor_width = 512;
 	dev->mode_config.cursor_height = 512;
-	dev->mode_config.preferred_depth = 24;
+	dev->mode_config.preferred_depth = 32;
 	dev->mode_config.helper_private = &vkms_mode_config_helpers;
 
 	return vkms_output_init(vkmsdev, 0);