platform/x86/amd/pmf: Use str_on_off() helper

We have a common helper to represent a boolean value as "on"/"off"
string. Use it for the sake of the unified style.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Link: https://lore.kernel.org/r/20230811131330.71263-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Hans de Goede <hdegoede@redhat.com>