iio: amplifiers: ad8366: refactor include headers

iio: amplifiers: ad8366: refactor include headers

Apply IWYU principle, removing the following headers:
- linux/device.h: no usage of devm_add_action_or_reset, device_attr...
- linux/kernel.h: no usage of container_of, kasprintf, ...
- linux/slab.h: memory management handled by iio
- linux/sysfs.h: sysfs interaction is managed by iio
- linux/iio/sysfs.h: not using iio device attributes in this driver
Adding the following missing headers:
+ linux/array_size.h: for ARRAY_SIZE
+ linux/bits.h: for BIT
+ linux/dev_printk.h: for dev_err
+ linux/math.h: for abs
+ linux/mutex.h: for mutex_lock, mutex_unlock
+ linux/mod_devicetable.h: for spi_device_id
+ linux/types.h for NULL, __aligned

Additionally, those include directives are alphabetically sorted.

Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>