[S390] lockdep: fix compile bug

arch/s390/kernel/built-in.o: In function `cleanup_io_leave_insn':
mem_detect.c:(.text+0x10592): undefined reference to `lockdep_sys_exit'

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/entry.S

@@ -1116,6 +1116,8 @@ cleanup_io_leave_insn:
 .Ltrace_irq_on: .long	trace_hardirqs_on
 .Ltrace_irq_off:
 		.long	trace_hardirqs_off
+#endif
+#ifdef CONFIG_LOCKDEP
 .Llockdep_sys_exit:
 		.long	lockdep_sys_exit
 #endif