hwmon: (pmbus/ibm-cffps) Fix the LED behavior when turned off

The driver should remain in control of the LED on the PSU, even while
off, not the PSU firmware as previously indicated.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/1576788607-13567-4-git-send-email-eajames@linux.ibm.com


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