[ARM] pxafb: fix the incorrect configuration of GPIO77 as ACBIAS for TFT LCD

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>
Tested-by: Alex Osborne <ato@meshy.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>