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/stm32f746-disco_defconfig b/configs/stm32f746-disco_defconfig
index a8edf11..dfbc766 100644
--- a/configs/stm32f746-disco_defconfig
+++ b/configs/stm32f746-disco_defconfig
@@ -53,7 +53,7 @@
 CONFIG_SPI=y
 CONFIG_DM_SPI=y
 CONFIG_STM32_QSPI=y
-CONFIG_DM_VIDEO=y
+CONFIG_VIDEO=y
 CONFIG_BACKLIGHT_GPIO=y
 CONFIG_VIDEO_STM32=y
 CONFIG_VIDEO_STM32_MAX_XRES=480