[S390] s390: hibernation support for s390

This patch introduces the hibernation backend support to the
s390 architecture. Now it is possible to suspend a mainframe Linux
guest using the following command:

echo disk > /sys/power/state

Signed-off-by: Hans-Joachim Picht <hans@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/suspend.h

@@ -0,0 +1,10 @@
+#ifndef __ASM_S390_SUSPEND_H
+#define __ASM_S390_SUSPEND_H
+
+static inline int arch_prepare_suspend(void)
+{
+	return 0;
+}
+
+#endif
+