s390/smp: add missing smp_store_status() for !SMP

Fix this compile error:

arch/s390/kernel/machine_kexec.c: In function ‘setup_regs’:
arch/s390/kernel/machine_kexec.c:63:3: error: implicit declaration
 of function ‘smp_store_status’ [-Werror=implicit-function-declaration]
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/smp.h

@@ -44,6 +44,7 @@ static inline void smp_call_online_cpu(void (*func)(void *), void *data)
 }
 
 static inline int smp_find_processor_id(int address) { return 0; }
+static inline int smp_store_status(int cpu) { return 0; }
 static inline int smp_vcpu_scheduled(int cpu) { return 1; }
 static inline void smp_yield_cpu(int cpu) { }
 static inline void smp_yield(void) { }