ARM: pxa: mainstone-wm97xx: use gpio lookup table

This driver hardcodes gpio numbers without a header file.
Use lookup tables instead.

Cc: Marek Vasut <marek.vasut@gmail.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-input@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>