tcg/aarch64: Fix generation of "scalar" vector operations

For some vector operations, "1D" is not a valid type, and there
are separate instructions for the 64-bit scalar operation.

Tested-by: Stefan Weil <sw@weilnetz.de>
Buglink: https://bugs.launchpad.net/qemu/+bug/1916112


Fixes: 14e4c1e2 ("tcg/aarch64: Add vector operations")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>