skiboot: Documentation typo in opal-return-cpu

changed OPAL_REINIT_CPU -> OPAL_REINIT_CPUS

Signed-off-by: Daniel Black <daniel.black@au.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

doc/opal-api/opal-return-cpu-69.rst

@@ -5,11 +5,11 @@ OPAL_RETURN_CPU
    int64_t opal_return_cpu(void);
 
 When OPAL first starts the host, all secondary CPUs are spinning in OPAL.
-To start them, one must call OPAL_START_CPU (you may want to OPAL_REINIT_CPU
+To start them, one must call OPAL_START_CPU (you may want to OPAL_REINIT_CPUS
 to set the HILE bit first).
 
 In cases where you need OPAL to do something for you across all CPUs, such
-as OPAL_REINIT_CPU, (on some platforms) a firmware update or get the machine
+as OPAL_REINIT_CPUS, (on some platforms) a firmware update or get the machine
 back into a similar state as to when the host OS was started (e.g. for kexec)
 you may also need to return control of the CPU to OPAL.