pmbus: (ibm-cffps) Add support for version 2 of the PSU

Version 2 of the PSU supports a second page of data and changes the
format of the FW version. Use the devicetree binding to differentiate
between the version the driver should use.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/1567192263-15065-4-git-send-email-eajames@linux.ibm.com


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