light on collie

Patch from Pavel Machek

Enable frontlight during collie bootup, so that display is actually
readable in anything other than bright sunlight.

Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
è”·~š