This is a revert of 428d2e82.

This is broken in the same manner as for VGA: trying to write to an
invalid address on the (currently 7-bit) i2c bus.

One notable failure appears to be for MacBooks. The scary part was that
it gave the appearance of working (i.e. reporting the absence of the
panel) on various all-in-one machines with ghost LVDS panels and not
failing for laptops.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Dave Airlie <airlied@linux.ie>
Signed-off-by: Keith Packard <keithp@keithp.com>