[PATCH] S390: Fix remaining ONE_DIRECTION warning messages

This patch fixes the remaining ONE_DIRECTION warnings for s390 specific conversions.
It defines ONE_DIRECTION to 0 like the patch from Steve Ellcey:
https://www.sourceware.org/ml/libc-alpha/2014-05/msg00039.html

    Changelog:
    * sysdeps/s390/s390-64/utf16-utf32-z9.c
    (ONE_DIRECTION): Define.
    * sysdeps/s390/s390-64/utf8-utf16-z9.c
    (ONE_DIRECTION): Define.
    * sysdeps/s390/s390-64/utf8-utf32-z9.c
    (ONE_DIRECTION): Define.