ARM: pxa: z2: use gpio lookup for audio device

The audio device is allocated by the audio driver, and it uses a gpio
number from the mach/z2.h header file.

Change it to use a gpio lookup table for the device allocated by the
driver to keep the header file local to the machine.

Acked-by: Mark Brown <broonie@kernel.org>
Cc: alsa-devel@alsa-project.org
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>