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/nitrogen6dl2g_defconfig b/configs/nitrogen6dl2g_defconfig
index 3d7027d..d1f7ec3 100644
--- a/configs/nitrogen6dl2g_defconfig
+++ b/configs/nitrogen6dl2g_defconfig
@@ -90,7 +90,7 @@
 CONFIG_CI_UDC=y
 CONFIG_USB_ETHER=y
 CONFIG_USB_ETH_CDC=y
-CONFIG_DM_VIDEO=y
+CONFIG_VIDEO=y
 CONFIG_SYS_WHITE_ON_BLACK=y
 CONFIG_I2C_EDID=y
 CONFIG_VIDEO_IPUV3=y