hwmon: (pmbus/ibm-cffps) Set the PMBUS_NO_CAPABILITY flag

Several power supplies supported by the IBM CFFPS driver don't
report valid data in the CAPABILITY register. This results in PEC
being enabled when it's not supported by the device, and since
the automatic version detection might fail, disable use of the
CAPABILITY register across the board for this driver.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20201222152640.27749-3-eajames@linux.ibm.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>