[S390] Add missing ifndef/define to include/asm-s390/sysinfo.h.

In order to protect against compile breakage in case the header file
gets included twice.

Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

include/asm-s390/sysinfo.h

···
  *		 Christian Borntraeger <[e-mail]>
  */
 
+#ifndef __ASM_S390_SYSINFO_H
+#define __ASM_S390_SYSINFO_H
+
 struct sysinfo_1_1_1 {
 	char reserved_0[32];
 	char manufacturer[16];
···
 		: "cc", "memory");
 	return r0;
 }
+
+#endif /* __ASM_S390_SYSINFO_H */