zen: rework lcd enable

The ZEN/ZEN-XFi seem to be very picky about the lcd. And they do not like
standby mode so I'm going to drop it, the OF doesn't use it anyway. I still
don't know what this "power" pin is about, obviously it's not real power but
the OF toggle it. Let's hope the lcd will finally become more stable with
fix: the driver now does full power on/off on enable/disable.

Change-Id: I1c465ee4f2462bc3d9507e5f575f0a181af60214
1 file changed