hwmon: (ntc_thermistor) Move and refactor DT parsing

hwmon: (ntc_thermistor) Move and refactor DT parsing

Move the parsing of the DT config right above probe().

Allocate the state container for the driver in probe()
instead of inside the DT config parsing function: as a
result return an int instead of a pointer.

Drop the check for !np: we can only probe from DT right
now so no risk of ending up here.

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/20211206020423.62402-1-linus.walleij@linaro.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>