Normally this is automatic in the size restrictions that are placed
on vector sizes coming from the implementation.  However, for the
legitimate size tuple [oprsz=8, maxsz=32], we need to clear the final
24 bytes of the vector register.  Without this check, do_dup selects
TCG_TYPE_V128 and clears only 16 bytes.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20180705191929.30773-2-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>