iio:adc:envelope-detector: Switch from of headers to mod_devicetable.h

There is nothing directly using of specific interfaces in this driver,
so lets not include the headers.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

drivers/iio/adc/envelope-detector.c

@@ -31,14 +31,13 @@
 #include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/mod_devicetable.h>
 #include <linux/mutex.h>
 #include <linux/iio/consumer.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
-#include <linux/of.h>
-#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>