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/gazerbeam_defconfig b/configs/gazerbeam_defconfig
index a432c05..b6698a5 100644
--- a/configs/gazerbeam_defconfig
+++ b/configs/gazerbeam_defconfig
@@ -218,7 +218,7 @@
 CONFIG_TPM_ATMEL_TWI=y
 CONFIG_TPM_AUTH_SESSIONS=y
 # CONFIG_TPM_V2 is not set
-CONFIG_DM_VIDEO=y
+CONFIG_VIDEO=y
 CONFIG_DISPLAY=y
 CONFIG_LOGICORE_DP_TX=y
 CONFIG_OSD=y