hwmon: (ntc_thermistor) Switch to generic firmware props

hwmon: (ntc_thermistor) Switch to generic firmware props

This switches to retrieveing the configuration of the NTC
from generic firmware properties so that we get neutral from
device tree: now ACPI or, more importantly, software nodes
can be used to spawn NTC devices provided they have the
required properties.

This was inspired by the similar changes made to the IIO
drivers.

This was tested on the Ux500 HREF with the NTC devices
probing from device tree just as fine after this as before.

Cc: Peter Rosin <peda@axentia.se>
Cc: Chris Lesiak <chris.lesiak@licor.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20211206020423.62402-2-linus.walleij@linaro.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>