S390: Move utf16-utf32-z9.c to multiarch folder and use s390_libc_ifunc_expr macro.

S390: Move utf16-utf32-z9.c to multiarch folder and use s390_libc_ifunc_expr macro.

The utf16-utf32-z9.c iconv module is using ifunc and thus the ifunc part should
be in multiarch folder.  Otherwise ifunc is used even if you configure
with --disable-multi-arch.

This patch moves the ifunc resolvers to the new file
sysdeps/s390/multiarch/utf16-utf32-z9.c. The resolvers are now implemented
with s390_libc_ifunc_expr macro instead of using gcc attribute ifunc directly.

The ifunc versions are implemented in sysdeps/s390/utf16-utf32-z9.c.
Each version is only implemented if needed or supported.  Therefore there is
a block at beginning of the file which selects the versions which should be
defined depending on support for multiarch, vector-support and used minimum
architecture level.  This block defines HAVE_[FROM|TO]_[C|VX] to 1 or 0.
The code below is rearranged and surrounded
by #if HAVE_[FROM|TO]_[C|VX] == 1.  There is no functional change.

ChangeLog:

	* sysdeps/s390/multiarch/utf16-utf32-z9.c: New File.
	* sysdeps/s390/utf16-utf32-z9.c: Move ifunc resolvers to multiarch
	folder and define ifunc versions depending on HAVE_[FROM|TO]_[C|VX].
	(HAVE_FROM_C, HAVE_FROM_VX, HAVE_TO_C, HAVE_TO_VX, FROM_LOOP_DEFAULT,
	FROM_LOOP_C, FROM_LOOP_VX, TO_LOOP_DEFAULT, TO_LOOP_C, TO_LOOP_VX):
	New Define.