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/configs/rock2_defconfig b/configs/rock2_defconfig
index ae432ad..6b86812 100644
--- a/configs/rock2_defconfig
+++ b/configs/rock2_defconfig
@@ -64,6 +64,7 @@
 CONFIG_DM_VIDEO=y
 CONFIG_DISPLAY=y
 CONFIG_VIDEO_ROCKCHIP=y
+CONFIG_DISPLAY_ROCKCHIP_HDMI=y
 CONFIG_CONSOLE_SCROLL_LINES=10
 CONFIG_USE_TINY_PRINTF=y
 CONFIG_CMD_DHRYSTONE=y