arm: mx6: cm-fx6: add support for displaytype env var

Add support for selecting display preset using the environment variable
"displaytype". This is a preparation for future merging of compulab
omap3_display.c display selection code with the cm-fx6 display selection code.

The "panel" environment variable is retained for backwards compatibility.

Cc: Stefano Babic <sbabic@denx.de>
Cc: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Acked-by: Igor Grinberg <grinberg@compulab.co.il>

board/compulab/cm_fx6/cm_fx6.c

@@ -95,7 +95,10 @@ int board_video_skip(void)
 {
 	int ret;
 	struct display_info_t *preset;
-	char const *panel = getenv("panel");
+	char const *panel = getenv("displaytype");
+
+	if (!panel) /* Also accept panel for backward compatibility */
+		panel = getenv("panel");
 
 	if (!panel)
 		return -ENOENT;