ASoC: max98396: Drop pointless include

This driver is already using solely GPIO descriptors and
do not need to include the legacy header <linux/gpio.h>.
Drop it.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230911-descriptors-asoc-max-v2-5-b9d793fb768e@linaro.org


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