zynqmp: pm: Implement pm_register_notifier PM API function

Signed-off-by: Anes Hadziahmetagic <anes.hadziahmetagic@aggios.com>
Signed-off-by: Filip Drazic <filip.drazic@aggios.com>
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>

plat/xilinx/zynqmp/pm_service/pm_api_sys.c

@@ -391,7 +391,12 @@ enum pm_ret_status pm_register_notifier(enum pm_node_id nid,
 					unsigned int wake,
 					unsigned int enable)
 {
-	return PM_RET_ERROR_NOTSUPPORTED;
+	uint32_t payload[PAYLOAD_ARG_CNT];
+
+	PM_PACK_PAYLOAD5(payload, PM_REGISTER_NOTIFIER,
+			 nid, event, wake, enable);
+
+	return pm_ipi_send(primary_proc, payload);
 }
 
 /**