Documentation/ABI/testing/sysfs-amd-pmf: Add ABI doc for AMD PMF

AMD PMF driver provides the flexibility to turn "on" or "off"
CnQF feature (introduced in the earlier patch).

Add corresponding ABI documentation for the new sysfs node and
also update MAINTAINERS file with this new information

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Link: https://lore.kernel.org/r/20220922131202.56529-4-Shyam-sundar.S-k@amd.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>