max20086-regulator.c needs <linux/gpio/consumer.h> for an enum, some
macros, and a function prototype. (seen on ARCH=m68k)

Adding this header file fixes multiple build errors:

../drivers/regulator/max20086-regulator.c: In function 'max20086_i2c_probe':
../drivers/regulator/max20086-regulator.c:217:26: error: storage size of 'flags' isn't known
  217 |         enum gpiod_flags flags;
../drivers/regulator/max20086-regulator.c:261:27: error: 'GPIOD_OUT_HIGH' undeclared (first use in this function); did you mean 'GPIOF_INIT_HIGH'?
  261 |         flags = boot_on ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
      |                           ^~~~~~~~~~~~~~
../drivers/regulator/max20086-regulator.c:261:44: error: 'GPIOD_OUT_LOW' undeclared (first use in this function); did you mean 'GPIOF_INIT_LOW'?
  261 |         flags = boot_on ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
../drivers/regulator/max20086-regulator.c:262:27: error: implicit declaration of function 'devm_gpiod_get'; did you mean 'devm_gpio_free'? [-Werror=implicit-function-declaration]
  262 |         chip->ena_gpiod = devm_gpiod_get(chip->dev, "enable", flags);
../drivers/regulator/max20086-regulator.c:217:26: warning: unused variable 'flags' [-Wunused-variable]
  217 |         enum gpiod_flags flags;

Fixes: bfff546a ("regulator: Add MAX20086-MAX20089 driver")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Watson Chow <watson.chow@avnet.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20220115033603.24473-1-rdunlap@infradead.orgSigned-off-by: Mark Brown <broonie@kernel.org>