ASoC: max9768: Convert to use GPIO descriptors

The MAX9768 is pretty straight forward to convert to GPIO
descriptors.

To name the GPIO properties, I looke at the bindings in
maxim,max9759.yaml which names these GPIO "mute" and
"shutdown" respectively.

No board files using platform data exist in the kernel, new
users can use GPIO descriptor tables if desired.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230825-descriptors-asoc-max-v1-1-b212292b2f08@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>