drm/rockchip: pass 0 to drm_fbdev_generic_setup()

Allow drm_fbdev_generic_setup() to pick the default bpp value for the
framebuffer.

This has no functional impact because the default is 32, given that
mode_config.preferred_depth is not set for Rockchip.
Suggested-by: NThomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: NJohn Keeping <john@metanate.com>
Signed-off-by: NThomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20211101114622.813536-1-john@metanate.com

drivers/gpu/drm/rockchip/rockchip_drm_drv.c

@@ -165,7 +165,7 @@ static int rockchip_drm_bind(struct device *dev)
 	if (ret)
 		goto err_kms_helper_poll_fini;
 
-	drm_fbdev_generic_setup(drm_dev, 32);
+	drm_fbdev_generic_setup(drm_dev, 0);
 
 	return 0;
 err_kms_helper_poll_fini: