HTU21 is now supported by IIO, and can be instantiated as hwmon driver
using the iio-hwmon bridge. An explicit hwmon driver is no longer needed.

Cc: William Markezana <william.markezana@meas-spec.com>
Cc: Ludovic Tancerel <ludovic.tancerel@maplehightech.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: NJean Delvare <jdelvare@suse.de>
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>