[ARM] 4594/1: ns9xxx: use the new gpio functions

Up to now only board-a9m9750dev.c used GPIOs.  It just wrote directly into the
corresponding registers.  Now it properly reserves the gpio and uses the API
function to configure it.

Signed-off-by: Uwe Kleine-König <ukleinek@informatik.uni-freiburg.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>