ARM: 7049/1: mach-sa1100: move SA1100 GPIO driver to GPIO subsystem

As per example from the other ARM boards, push the SA100
GPIO driver down to the GPIO subsystem so it can be consolidated.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>