Documentation: power: Remove info about non-existing QoS interfaces

cpu_latency_qos_add|remove_notifier() doesn't exist, hence let's drop
the documentation of them.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://patch.msgid.link/20250710102656.127654-1-ulf.hansson@linaro.org


Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>