hwmon: (pmbus) add MFR_* registers to debugfs

Add registers to debugfs:
PMBUS_MFR_ID
PMBUS_MFR_MODEL
PMBUS_MFR_REVISION
PMBUS_MFR_LOCATION
PMBUS_MFR_DATE
PMBUS_MFR_SERIAL

To reduce the number of debugfs entries, only values from page 0 are
reported. It is assumed that values of these registers are the same for
all pages. Please note that the PMBUS standard allows added registers to
be page-specific.

Signed-off-by: Adam Wujek <dev_public@wujek.eu>
Link: https://lore.kernel.org/r/20220601013232.801133-2-dev_public@wujek.eu


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