drm/rockchip: cdn-dp: add missing check in cdn_dp_config_video()

commit 46c31e1 upstream.

The result of cdn_dp_reg_write() is checked everywhere (with the error
being logged by the callers) except one place in cdn_dp_config_video().
Add the missing result check, bailing out early on error...

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

Fixes: 1a0f7ed ("drm/rockchip: cdn-dp: add cdn DP support for rk3399")
Signed-off-by: Sergey Shtylyov <s.shtylyov@auroraos.dev>
Cc: stable@vger.kernel.org
Reviewed-by: Chaoyi Chen <chaoyi.chen@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/adf6b313-f7db-4d8f-9000-8c65446ba041@auroraos.dev
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Sergey Shtylyov

drivers/gpu/drm/rockchip/cdn-dp-reg.c

@@ -683,6 +683,8 @@ int cdn_dp_config_video(struct cdn_dp_device *dp)
 	val = div_u64(8 * (symbol + 1), bit_per_pix) - val;
 	val += 2;
 	ret = cdn_dp_reg_write(dp, DP_VC_TABLE(15), val);
+	if (ret)
+		goto err_config_video;
 
 	switch (video->color_depth) {
 	case 6: