A given RISU testcase for SVE can produce
tcg-op-vec.c:511: do_shifti: Assertion `i >= 0 && i < (8 << vece)' failed.
because expand_vec_sari gave a shift count of 32 to a MO_32
vector shift.
In 44f1441dbe1, we changed from direct expansion of vector opcodes
to re-use of the tcg expanders. So while the comment correctly notes
that the hw will handle such a shift count, we now have to take our
own sanity checks into account. Which is easy in this particular case.
Fixes: 44f1441dbe1
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>