s390/crash dump: add missing SMP dependency

Fix this:
arch/s390/kernel/crash_dump.c:296:14:
  error: 'zfcpdump_save_areas' undeclared (first use in this function)

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

arch/s390/Kconfig

@@ -569,7 +569,7 @@ config KEXEC
 
 config CRASH_DUMP
 	bool "kernel crash dumps"
-	depends on 64BIT
+	depends on 64BIT && SMP
 	select KEXEC
 	help
 	  Generate crash dump after being started by kexec.