video: Add an enum for active low/high

This is used for video signals in some drivers so provide a standard way
of representing it in an enum.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>

include/video.h

@@ -23,6 +23,11 @@ struct video_uc_platdata {
 	ulong base;
 };
 
+enum video_polarity {
+	VIDEO_ACTIVE_HIGH,	/* Pins are active high */
+	VIDEO_ACTIVE_LOW,	/* Pins are active low */
+};
+
 /*
  * Bits per pixel selector. Each value n is such that the bits-per-pixel is
  * 2 ^ n