hwmon: (iio_hwmon) Drop bogus __refdata annotation

As the IIO hardware monitoring driver does not have any code or data
located in initmem, there is no need to annotate the iio_hwmon_driver
structure with __refdata.  Drop the annotation, to avoid suppressing
future section warnings.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20201211133512.2969952-1-geert+renesas@glider.be


Signed-off-by: Guenter Roeck <linux@roeck-us.net>