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/sandbox64_defconfig b/configs/sandbox64_defconfig
index 0475672..625a1aa 100644
--- a/configs/sandbox64_defconfig
+++ b/configs/sandbox64_defconfig
@@ -226,7 +226,7 @@
 CONFIG_USB=y
 CONFIG_USB_EMUL=y
 CONFIG_USB_KEYBOARD=y
-CONFIG_DM_VIDEO=y
+CONFIG_VIDEO=y
 CONFIG_CONSOLE_ROTATION=y
 CONFIG_CONSOLE_TRUETYPE=y
 CONFIG_CONSOLE_TRUETYPE_CANTORAONE=y