video: Enable VIDEO_ANSI by default only with EFI

This is not generally needed unless EFI_LOADER is used. Adjust the default
setting to reduce the size of the U-Boot build.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index f539977..440b161 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -112,10 +112,13 @@
 
 config VIDEO_ANSI
 	bool "Support ANSI escape sequences in video console"
-	default y
+	default y if EFI_LOADER
 	help
 	  Enable ANSI escape sequence decoding for a more fully functional
-	  console.
+	  console. Functionality includes changing the text colour and moving
+	  the cursor. These date from the 1970s and are still widely used today
+	  to control a text terminal. U-Boot implements these by decoding the
+	  sequences and performing the appropriate operation.
 
 config VIDEO_MIPI_DSI
 	bool "Support MIPI DSI interface"