S390: Implement bzero with memset.

S390: Implement bzero with memset.

This patch removes the bzero s390 implementation with mvcle and
adds entry points for bzero in memset ifunc variants.
Therefore an ifunc resolver is implemented for bzero, too.

ChangeLog:

	* sysdeps/s390/s390-32/bzero.S: Delete file.
	* sysdeps/s390/s390-64/bzero.S: Likewise.
	* sysdeps/s390/Makefile (sysdep_routines): Add bzero.
	* sysdeps/s390/bzero.c: New file.
	* sysdeps/s390/memset-z900.S: Add bzero entry points.
	* sysdeps/s390/ifunc-memset.h: Add bzero function macros.
	* sysdeps/s390/multiarch/ifunc-impl-list.c
	(__libc_ifunc_impl_list): Add bzero ifunc variants.