regulator: mcp16502: Include linux/gpio/consumer.h to fix build error

Fix below build error:
drivers/regulator/mcp16502.c: In function ‘mcp16502_gpio_set_mode’:
drivers/regulator/mcp16502.c:135:3: error: implicit declaration of function ‘gpiod_set_value’; did you mean ‘gpio_set_value’? [-Werror=implicit-function-declaration]
   gpiod_set_value(mcp->lpm, 0);
   ^~~~~~~~~~~~~~~
   gpio_set_value
drivers/regulator/mcp16502.c: In function ‘mcp16502_probe’:
drivers/regulator/mcp16502.c:486:13: error: implicit declaration of function ‘devm_gpiod_get’; did you mean ‘devm_gpio_free’? [-Werror=implicit-function-declaration]
  mcp->lpm = devm_gpiod_get(dev, "lpm", GPIOD_OUT_LOW);
             ^~~~~~~~~~~~~~
             devm_gpio_free
drivers/regulator/mcp16502.c:486:40: error: ‘GPIOD_OUT_LOW’ undeclared (first use in this function); did you mean ‘GPIOF_INIT_LOW’?
  mcp->lpm = devm_gpiod_get(dev, "lpm", GPIOD_OUT_LOW);
                                        ^~~~~~~~~~~~~
                                        GPIOF_INIT_LOW
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/mcp16502.c

@@ -17,6 +17,7 @@
 #include <linux/regmap.h>
 #include <linux/regulator/driver.h>
 #include <linux/suspend.h>
+#include <linux/gpio/consumer.h>
 
 #define VDD_LOW_SEL 0x0D
 #define VDD_HIGH_SEL 0x3F