iio: Remove kernel-doc keyword in file header comment

Remove kernel-doc keyword from function header comment.
It fixes issues spotted by scripts/kernel-doc like:
drivers/iio/<driver>.c:3: info: Scanning doc for function <component name>
drivers/iio/<driver>.c:X: warning: expecting prototype for <component name>.
  Prototype was for <function>() instead

To reproduce the errors:
scripts/kernel-doc -v -none $(find drivers/iio/ -name \*.c \
-exec head -2 {} \+ | grep -B2 -e '\*\*' | grep '==' | cut -d ' ' -f 2)

After, confirm these errors are gone with:
scripts/kernel-doc -v -none $(git show --name-only  | grep -e "^driver")
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Link: https://lore.kernel.org/r/20210309234314.2208256-1-gwendal@chromium.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/bma220_spi.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * BMA220 Digital triaxial acceleration sensor driver
  *
  * Copyright (c) 2016,2020 Intel Corporation.

drivers/iio/accel/da280.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * IIO driver for the MiraMEMS DA280 3-axis accelerometer and
  * IIO driver for the MiraMEMS DA226 2-axis accelerometer
  *

drivers/iio/accel/da311.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * IIO driver for the MiraMEMS DA311 3-axis accelerometer
  *
  * Copyright (c) 2016 Hans de Goede <hdegoede@redhat.com>

drivers/iio/accel/dmard10.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * IIO driver for the 3-axis accelerometer Domintech ARD10.
  *
  * Copyright (c) 2016 Hans de Goede <hdegoede@redhat.com>

drivers/iio/accel/mc3230.c

 // SPDX-License-Identifier: GPL-2.0-or-later
-/**
+/*
  * mCube MC3230 3-Axis Accelerometer
  *
  * Copyright (c) 2016 Hans de Goede <hdegoede@redhat.com>

drivers/iio/accel/mma7660.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Freescale MMA7660FC 3-Axis Accelerometer
  *
  * Copyright (c) 2016, Intel Corporation.

drivers/iio/accel/stk8312.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Sensortek STK8312 3-Axis Accelerometer
  *
  * Copyright (c) 2015, Intel Corporation.

drivers/iio/accel/stk8ba50.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Sensortek STK8BA50 3-Axis Accelerometer
  *
  * Copyright (c) 2015, Intel Corporation.

drivers/iio/adc/ti-adc084s021.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (C) 2017 Axis Communications AB
  *
  * Driver for Texas Instruments' ADC084S021 ADC chip.

drivers/iio/humidity/am2315.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Aosong AM2315 relative humidity and temperature
  *
  * Copyright (c) 2016, Intel Corporation.

drivers/iio/light/opt3001.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * opt3001.c - Texas Instruments OPT3001 Light Sensor
  *
  * Copyright (C) 2014 Texas Instruments Incorporated - https://www.ti.com

drivers/iio/light/stk3310.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Sensortek STK3310/STK3311 Ambient Light and Proximity Sensor
  *
  * Copyright (c) 2015, Intel Corporation.

drivers/iio/trigger/iio-trig-hrtimer.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * The industrial I/O periodic hrtimer trigger driver
  *
  * Copyright (C) Intuitive Aerial AB