ARM: 6641/1: ep93xx: implement gpiolib set_debounce for built-in GPIOs

GPIO Ports A, B, and F on the ep93xx provide interrupt capability.  It
is possible to debounce the input signal on these ports when interrupts
are enabled.

Support for this debounce capability was provided with an ep93xx internal
function.  Now that gpiolib knows about gpio debounce, use the gpiolib
method and do not export the internal function.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Ryan Mallon <ryan@bluewatersys.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>