s390x/tcg: Simplify vop64_2() handling

Let's rework our macros and simplify. We still need helper functions in
most cases due to the different parameters types.

Next, we'll only have 32/128bit variants for vfi and vfsq, so special
case the others.

Note that for vfsq, the XxC and erm passed in the simd_data() will never be
set, resulting in the same behavior.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210608092337.12221-5-david@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>