tcg/i386: Fix encoding of OPC_VPSRAQ for INDEX_op_sars_vec

We wanted the VPSRAQ variant with the scalar vector shift operand,
not the variant with an immediate operand.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1022


Fixes: 47b331b2 ("tcg/i386: Implement avx512 scalar shift")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>