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/nyan-big_defconfig b/configs/nyan-big_defconfig
index 6607edd..e55da6e 100644
--- a/configs/nyan-big_defconfig
+++ b/configs/nyan-big_defconfig
@@ -98,7 +98,7 @@
 CONFIG_USB_GADGET_PRODUCT_NUM=0x701a
 CONFIG_CI_UDC=y
 CONFIG_USB_GADGET_DOWNLOAD=y
-CONFIG_DM_VIDEO=y
+CONFIG_VIDEO=y
 # CONFIG_VIDEO_BPP8 is not set
 # CONFIG_VIDEO_BPP32 is not set
 CONFIG_DISPLAY=y