hwmon: (adm9240) Create functions for updating measure and config

Split the body of adm9240_update_device() into two helper functions
adm9240_update_measure() and adm9240_update_config(). Although neither
of the new helpers returns an error yet lay the groundwork for
propagating failures through to the sysfs readers.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20200924085102.15219-3-chris.packham@alliedtelesis.co.nz


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