S390: Unify 31/64bit memset.

S390: Unify 31/64bit memset.

The implementation of memset for s390-32 (31bit) and
s390-64 (64bit) is nearly the same.
This patch unifies it for maintability reasons.

__memset_z10 and __memset_z196 differs between 31 and 64bit:
-31bit needs .machinemode "zarch_nohighgprs" and llgfr   %r4,%r4
-lr vs lgr and some other instructions:
But lgr and co can be also used on 31bit as this ifunc variant
is only called if we are on a zarch machine.

__memset_default differs between 31 and 64bit:
-Some 31bit vs 64bit instructions (e.g. ltr vs ltgr.
Solved with 31/64 specific instruction macros).
-The address of mvc instruction is setup in different ways
(larl vs bras). Solved with #if defined __s390x__.

Otherwise 31/64bit implementation has the same structure of the code.

ChangeLog:

	* sysdeps/s390/s390-64/memset.S: Move to ...
	* sysdeps/s390/memset.S: ... here.
	Adjust to be usable for 31/64bit.
	* sysdeps/s390/s390-32/memset.S: Delete File.
	* sysdeps/s390/multiarch/Makefile (sysdep_routines): Add memset.
	* sysdeps/s390/s390-32/multiarch/Makefile (sysdep_routines):
	Remove memset.
	* sysdeps/s390/s390-64/multiarch/Makefile: Likewise.
	* sysdeps/s390/s390-64/multiarch/memset-s390x.S: Move to ...
	* sysdeps/s390/multiarch/memset-s390x.S: ... here.
	Adjust to be usable for 31/64bit.
	* sysdeps/s390/s390-32/multiarch/memset-s390.S: Delete File.
	* sysdeps/s390/s390-64/multiarch/memset.c: Move to ...
	* sysdeps/s390/multiarch/memset.c: ... here.
	* sysdeps/s390/s390-32/multiarch/memset.c: Delete File.