bsps/irq: fix resource leak in irq-server.c

Resource leak identified by Coverity (CID 1456675). The value
of instances is leaked in case some but not all irq servers are
created. It should be stored in bsp_interrupt_server_instances.

bsps/shared/irq/irq-server.c

@@ -539,6 +539,7 @@ rtems_status_code rtems_interrupt_server_initialize(
 
 #if defined(RTEMS_SMP)
       if (cpu_index > 0) {
+        bsp_interrupt_server_instances = instances;
         return RTEMS_SUCCESSFUL;
       }