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/spring_defconfig b/configs/spring_defconfig
index 693ee54..0cc0556 100644
--- a/configs/spring_defconfig
+++ b/configs/spring_defconfig
@@ -91,7 +91,7 @@
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_HOST_ETHER=y
 CONFIG_USB_ETHER_ASIX88179=y
-CONFIG_DM_VIDEO=y
+CONFIG_VIDEO=y
 # CONFIG_VIDEO_BPP8 is not set
 CONFIG_VIDCONSOLE_AS_LCD=y
 CONFIG_DISPLAY=y