hwmon: (pmbus/mp2888) Fix sensors readouts for MPS Multi-phase mp2888 controller

hwmon: (pmbus/mp2888) Fix sensors readouts for MPS Multi-phase mp2888 controller

Fix scale factors for reading MPS Multi-phase mp2888 controller.
Fixed sensors:
    - PIN/POUT: based on vendor documentation, set bscale factor 0.5W/LSB
    - IOUT: based on vendor documentation, set scale factor 0.25 A/LSB

Fixes: e4db7719d037 ("hwmon: (pmbus) Add support for MPS Multi-phase mp2888 controller")
Signed-off-by: Oleksandr Shamray <oleksandrs@nvidia.com>
Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
Link: https://lore.kernel.org/r/20220929121642.63051-1-oleksandrs@nvidia.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>