hwmon: (adm9240) Use loops to avoid duplicated code

Use loops for reading temp_max and initialising FAN_MIN/TEMP_MAX rather
than duplicating code.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20200924085102.15219-2-chris.packham@alliedtelesis.co.nz


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