[S390] cpu topology support for s390.

Add s390 backend so we can give the scheduler some hints about the
cpu topology.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/include/asm-s390/smp.h b/include/asm-s390/smp.h
index c7b7432..a464a66 100644
--- a/include/asm-s390/smp.h
+++ b/include/asm-s390/smp.h
@@ -90,6 +90,8 @@
 extern void cpu_die (void) __attribute__ ((noreturn));
 extern int __cpu_up (unsigned int cpu);
 
+extern struct mutex smp_cpu_state_mutex;
+
 extern int smp_call_function_mask(cpumask_t mask, void (*func)(void *),
 	void *info, int wait);
 #endif