Documentation: admin-guide: pm: Add efficiency vs. latency tradeoff to uncore documentation

Added documentation about the functionality of efficiency vs. latency tradeoff
control in intel Xeon processors, and how this is configured via sysfs.

Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240828153657.1296410-2-tero.kristo@linux.intel.com


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