hwmon: (ntc_thermistor) Drop unused headers.

hwmon: (ntc_thermistor) Drop unused headers.

The IIO usage in this driver is purely consumer so it should only
be including linux/iio/consumer.h  Whilst here drop pm_runtime.h
as there is no runtime power management in the driver.

Found using include-what-you-use and manual inspection of the
suggestions.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210611142257.103094-1-jic23@kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>