Missing the segment prefix means that user-only fails
to add guest_base for some 128-bit load/store.
Fixes: 098d0fc10d2 ("tcg/i386: Support 128-bit load/store")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1763
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>