hwmon: (adt7475) set start bit in probe

The ADT7475 and ADT7476 have the STRT bit cleared by default[1]. Before any
monitoring activities the STRT bit needs to be set. Logically this needs
to happen before any of the sensors are read so the probe() function
seems the best place for it.

[1] - https://www.onsemi.com/pub/Collateral/ADT7475-D.PDF



Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>