video: Rename CONFIG_DM_VIDEO to CONFIG_VIDEO

Now that all the old code is gone, rename this option. Driver model
migration is now complete.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/chromebook_bob_defconfig b/configs/chromebook_bob_defconfig
index d81129a..6ebd53e 100644
--- a/configs/chromebook_bob_defconfig
+++ b/configs/chromebook_bob_defconfig
@@ -110,7 +110,7 @@
 CONFIG_USB_ETHER_MCS7830=y
 CONFIG_USB_ETHER_RTL8152=y
 CONFIG_USB_ETHER_SMSC95XX=y
-CONFIG_DM_VIDEO=y
+CONFIG_VIDEO=y
 CONFIG_DISPLAY=y
 CONFIG_VIDEO_ROCKCHIP=y
 CONFIG_VIDEO_ROCKCHIP_MAX_XRES=1280