iio: adc: palmas: Remove the unneeded include <linux/i2c.h>

This driver does not use i2c, so there is no point in including
<linux/i2c.h>

Remove it.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/9d23cd04d7f99dc8d813584aae5268b57f92fcd8.1682320298.git.christophe.jaillet@wanadoo.frSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/palmas_gpadc.c

@@ -14,7 +14,6 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
-#include <linux/i2c.h>
 #include <linux/pm.h>
 #include <linux/mfd/palmas.h>
 #include <linux/completion.h>