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.fr


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>