ASoC: max98396: Fix build error for implicit function declaration

sound/soc/codecs/max98396.c: In function ‘max98396_i2c_probe’:
sound/soc/codecs/max98396.c:1555:25: error: implicit declaration of function ‘devm_gpiod_get_optional’; did you mean ‘devm_regulator_get_optional’? [-Werror=implicit-function-declaration]
  max98396->reset_gpio = devm_gpiod_get_optional(&i2c->dev,
                         ^~~~~~~~~~~~~~~~~~~~~~~
                         devm_regulator_get_optional
sound/soc/codecs/max98396.c:1556:23: error: ‘GPIOD_OUT_HIGH’ undeclared (first use in this function); did you mean ‘GPIOF_INIT_HIGH’?
              "reset", GPIOD_OUT_HIGH);
                       ^~~~~~~~~~~~~~
                       GPIOF_INIT_HIGH
sound/soc/codecs/max98396.c:1556:23: note: each undeclared identifier is reported only once for each function it appears in
sound/soc/codecs/max98396.c:1565:3: error: implicit declaration of function ‘gpiod_set_value_cansleep’; did you mean ‘gpio_set_value_cansleep’? [-Werror=implicit-function-declaration]
   gpiod_set_value_cansleep(max98396->reset_gpio, 0);
   ^~~~~~~~~~~~~~~~~~~~~~~~
   gpio_set_value_cansleep
cc1: all warnings being treated as errors

Include header file <linux/gpio/consumer.h>

Fixes: b5858113

 ("ASoC: max98396: add amplifier driver")
Signed-off-by: Hui Tang <tanghui20@huawei.com>
Link: https://lore.kernel.org/r/20220512074640.75550-2-tanghui20@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>