Add registers to debugfs:
PMBUS_MFR_ID
PMBUS_MFR_MODEL
PMBUS_MFR_REVISION
PMBUS_MFR_LOCATION
PMBUS_MFR_DATE
PMBUS_MFR_SERIAL
PMBUS_IC_DEVICE_REV
Signed-off-by: Adam Wujek <dev_public@wujek.eu>