ARM: pxa/lubbock: add GPIO driver for LUB_MISC_WR register

Add a gpio driver for the lubbock miscellaneous write IO register so we
can take advantage of subsystems modelled around gpiolib, rather than
having to provide platform specific callbacks.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>