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.