hwmon: (pmbus/core) Add support for Intel IMVP9 and AMD 6.25mV modes

Extend "vrm_version" with the type for Intel IMVP9 and AMD 6.25mV VID
modes.
Add calculation for those types.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Link: https://lore.kernel.org/r/20200113150841.17670-3-vadimp@mellanox.com


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