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/arch/arm/mach-imx/cpu.c b/arch/arm/mach-imx/cpu.c
index ba386c2..702cfc3 100644
--- a/arch/arm/mach-imx/cpu.c
+++ b/arch/arm/mach-imx/cpu.c
@@ -310,7 +310,7 @@
 	/* disable video before launching O/S */
 	ipuv3_fb_shutdown();
 #endif
-#if defined(CONFIG_VIDEO_MXS) && !defined(CONFIG_DM_VIDEO)
+#if defined(CONFIG_VIDEO_MXS) && !defined(CONFIG_VIDEO)
 	lcdif_power_down();
 #endif
 }