sysdev: fix missing s390 conversion

In linux-next "sysdev: Pass attribute in sysdev_class attributes show/store"
forgot to convert one place in s390 code. Here is the missing part.

Cc: Andi Kleen <ak@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>