cmd/asm: add KMA and KMCTR instructions on s390x.

cmd/asm: add KMA and KMCTR instructions on s390x.

This CL is to add assembly instruction mnemonics for the following instructions, mainly used in crypto packages.

 * KMA    - cipher message with authentication
 * KMCTR  - cipher message with counter

Fixes #61163

Change-Id: Iff9a69911aeb4fab4bca8755b23a106eaebb2332
Reviewed-on: https://go-review.googlesource.com/c/go/+/515195
Reviewed-by: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>