Documentation: admin-guide: PM: Fix two typos

Fix two typos in the admin-guide:

 - a missing e in "reference_perf" in cppc_sysfs.rst.
 - the amd_pstate sysfs path uses a dash instead of an underscore.
Signed-off-by: Erwan Velu <e.velu@criteo.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/admin-guide/acpi/cppc_sysfs.rst

@@ -75,4 +75,4 @@ taking two different snapshots of feedback counters at time T1 and T2.
   delivered_counter_delta = fbc_t2[del] - fbc_t1[del]
   reference_counter_delta = fbc_t2[ref] - fbc_t1[ref]
 
-  delivered_perf = (refernce_perf x delivered_counter_delta) / reference_counter_delta
+  delivered_perf = (reference_perf x delivered_counter_delta) / reference_counter_delta

Documentation/admin-guide/pm/amd-pstate.rst

@@ -361,7 +361,7 @@ Global Attributes
 
 ``amd-pstate`` exposes several global attributes (files) in ``sysfs`` to
 control its functionality at the system level.  They are located in the
-``/sys/devices/system/cpu/amd-pstate/`` directory and affect all CPUs.
+``/sys/devices/system/cpu/amd_pstate/`` directory and affect all CPUs.
 
 ``status``
 	Operation mode of the driver: "active", "passive" or "disable".