system/nxinit: fix missing blank line after declaration in service.c

nxstyle flags a missing blank line between the declaration of "s" and
the first statement in option_reboot_on_failure(); pre-existing,
unrelated to any behavioral change here.

Assisted-by: Kiro:claude-sonnet-5
Signed-off-by: wangjianyu3 <wangjianyu3@xiaomi.com>

system/nxinit/service.c

@@ -279,6 +279,7 @@ static int option_reboot_on_failure(FAR struct service_manager_s *sm,
 {
   FAR struct service_s *s = list_last_entry(&sm->services, struct service_s,
                                             node);
+
   s->reset_reason = atoi(argv[1]);
   return 0;
 }