Add missed fields in documentation of plat_psci_ops

Change-Id: Ie4ee8aa2627573c95549927c9ac4e8a963035359
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>

docs/platform-migration-guide.rst

@@ -158,6 +158,12 @@ for the ``plat_psci_ops`` structure which is declared as :
         int (*validate_ns_entrypoint)(unsigned long ns_entrypoint);
         void (*get_sys_suspend_power_state)(
                         psci_power_state_t *req_state);
+        int (*get_pwr_lvl_state_idx)(plat_local_state_t pwr_domain_state,
+                                    int pwrlvl);
+        int (*translate_power_state_by_mpidr)(u_register_t mpidr,
+                                    unsigned int power_state,
+                                    psci_power_state_t *output_state);
+        int (*get_node_hw_state)(u_register_t mpidr, unsigned int power_level);
     } plat_psci_ops_t;
 
 The description of these handlers can be found in the `Porting Guide <porting-guide.rst#user-content-function--plat_setup_psci_ops-mandatory>`__.