rockchip: video: Kconfig: Add Kconfig for rockchip video driver

1. add Kconfig for rockchip video driver, so that video port can be
selected as needed.
2. move VIDEO_ROCKCHIP option to new Kconfig for concision.

Signed-off-by: Eric Gao <eric.gao@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>
Drop indenting in Kconfig:
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index e29c3fc..446cca9 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -425,15 +425,7 @@
 	 Set maximum framebuffer size to be used for Freescale Display
 	 Controller Unit (DCU4).
 
-config VIDEO_ROCKCHIP
-	bool "Enable Rockchip video support"
-	depends on DM_VIDEO
-	help
-	   Rockchip SoCs provide video output capabilities for High-Definition
-	   Multimedia Interface (HDMI), Low-voltage Differential Signalling
-	   (LVDS), embedded DisplayPort (eDP) and Display Serial Interface
-	   (DSI). This driver supports the on-chip video output device, and
-	   targets the Rockchip RK3288.
+source "drivers/video/rockchip/Kconfig"
 
 config VIDEO_SANDBOX_SDL
 	bool "Enable sandbox video console using SDL"