iio: Remove unused declarations

iio: Remove unused declarations

Commit 0f3a8c3f34f7 ("iio: Add support for creating IIO devices via configfs")
declared but never implemented iio_sw_device_type_configfs_{un}register().
Commit b662f809d410 ("iio: core: Introduce IIO software triggers") declared but
never implemented iio_sw_trigger_type_configfs_{un}register().
Commit a3e0b51884ee ("iio: accel: add support for FXLS8962AF/FXLS8964AF accelerometers")
declared but never implemented fxls8962af_core_remove().
Commit 8dedcc3eee3a ("iio: core: centralize ioctl() calls to the main chardev")
declared but never implemented iio_device_ioctl().

Commit d430f3c36ca6 ("iio: imu: inv_mpu6050: Use regmap instead of i2c specific functions")
removed inv_mpu6050_write_reg() but not its declaration.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20230811095701.35372-1-yuehaibing@huawei.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>