iio: adc: ad7768-1: reorganize driver headers

Remove kernel.h since it adds a lot of unnecessary dependencies.
Add specific headers to ensure all functions and macros used in the driver
are directly declared.

Suggested-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patch.msgid.link/1f7677d31a0165cb30d7eb3b4d613e1337937f9a.1746662899.git.Jonathan.Santos@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: jonathanns

drivers/iio/adc/ad7768-1.c

@@ -4,13 +4,15 @@
  *
  * Copyright 2017 Analog Devices Inc.
  */
+#include <linux/array_size.h>
 #include <linux/bitfield.h>
 #include <linux/clk.h>
+#include <linux/completion.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/gpio/consumer.h>
-#include <linux/kernel.h>
+#include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>