hwmon: (max31785) Add OF device ID table

The driver doesn't have a struct of_device_id table but supported devices
are registered via Device Trees. This is working on the assumption that a
I2C device registered via OF will always match a legacy I2C device ID and
that the MODALIAS reported will always be of the form i2c:<device>.

But this could change in the future so the correct approach is to have an
OF device ID table if the devices are registered via OF.

Before this patch:

$ modinfo drivers/hwmon/pmbus/max31785.ko | grep alias
alias:          i2c:max31785a
alias:          i2c:max31785

After this patch:

$ modinfo drivers/hwmon/pmbus/max31785.ko | grep alias
alias:          i2c:max31785a
alias:          i2c:max31785
alias:          of:N*T*Cmaxim,max31785aC*
alias:          of:N*T*Cmaxim,max31785a
alias:          of:N*T*Cmaxim,max31785C*
alias:          of:N*T*Cmaxim,max31785

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>