A galois field multiplication in field 2 is like binary multiplication,
however instead of doing ordinary binary additions, xor's are performed.
So no carries are considered.
Implement all variants via helpers. s390_vec_sar() and s390_vec_shr()
will be reused later on.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
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