board: ge: bx50v3: enable backlight on demand

Enable display backlight only if a message needs to be displayed.
The kernel re-initializes the backlight, which results in some
unwanted artifacts.

Signed-off-by: Ian Ray <ian.ray@ge.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

include/configs/ge_bx50v3.h

@@ -128,6 +128,7 @@
 	"swappartitions=" \
 		"setexpr partnum 3 - ${partnum}\0" \
 	"failbootcmd=" \
+		"bx50_backlight_enable; " \
 		"msg=\"Monitor failed to start.  Try again, or contact GE Service for support.\"; " \
 		"echo $msg; " \
 		"setenv stdout vga; " \