services: Fix pmr_el1 rewrote issue in sdei_disaptch_event()

Consider a RAS scenario:
Enter EL3 by sync exception, then call spm_mm_sp_call() enter
EL0s to handle this error, then call sdei_dispatch_event() to
inform OS. Finally, return back to OS from sync exception flow.
Similar flow is sgi_ras_intr_handler() in sgi_ras.c.

The icc_pmr_el1 register will be change in above flow:
1 cm_el1_sysregs_context_save(NON_SECURE);
  -> ehf_exited_normal_world();
    ##icc_pmr_el1: 0xf8 => 0x80
2 spm_mm_sp_call();
3 sdei_dispatch_event();
4 ehf_activate_priority(sdei_event_priority(map));
    ##icc_pmr_el1: 0x80 => 0x60
5 restore_and_resume_ns_context();
  -> ehf_exited_normal_world();
     ##return due to has_valid_pri_activations(pe_data) == 1
6 ehf_deactivate_priority(sdei_event_priority(map));
    ##icc_pmr_el1: 0x60 => 0x80
The icc_pmr_el1 was rewrote from 0xf8 to 0x80. This issue will
result in OS hang when eret to OS from RAS flow.

Move ehf_activate_priority(sdei_event_priority(map)) after
restore_and_resum...

services/std_svc/sdei/sdei_intr_mgmt.c

@@ -636,15 +636,15 @@ int sdei_dispatch_event(int ev_num)
 	if (!can_sdei_state_trans(se, DO_DISPATCH))
 		return -1;
 
-	/* Activate the priority corresponding to the event being dispatched */
-	ehf_activate_priority(sdei_event_priority(map));
-
 	/*
 	 * Prepare for NS dispatch by restoring the Non-secure context and
 	 * marking that as active.
 	 */
 	ns_ctx = restore_and_resume_ns_context();
 
+	/* Activate the priority corresponding to the event being dispatched */
+	ehf_activate_priority(sdei_event_priority(map));
+
 	/* Dispatch event synchronously */
 	setup_ns_dispatch(map, se, ns_ctx, &dispatch_jmp);
 	begin_sdei_synchronous_dispatch(&dispatch_jmp);