ASoC: ak4118: fix missing header

This driver use the gpio consumer interface.
Add the header as it's needed.
Signed-off-by: Clément Péron <peron.clem@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/ak4118.c

@@ -6,6 +6,7 @@
  */
 
 #include <linux/i2c.h>
+#include <linux/gpio/consumer.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/of_gpio.h>