s390/zfcpdump: make zfcpdump depend on 64BIT

Get rid of this link error:

arch/s390/built-in.o: In function `smp_prepare_cpus':
(.init.text+0x301e): undefined reference to `dump_save_area_create'
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -596,7 +596,7 @@ config CRASH_DUMP
 config ZFCPDUMP
 	def_bool n
 	prompt "zfcpdump support"
-	depends on SMP
+	depends on 64BIT && SMP
 	help
 	  Select this option if you want to build an zfcpdump enabled kernel.
 	  Refer to <file:Documentation/s390/zfcpdump.txt> for more details on this.