target/arm: Fix cpu_get_tb_cpu_state() for non-SVE CPUs

target/arm: Fix cpu_get_tb_cpu_state() for non-SVE CPUs

Not only are the sve-related tb_flags fields unused when SVE is
disabled, but not all of the cpu registers are initialized properly
for computing same.  This can corrupt other fields by ORing in -1,
which might result in QEMU crashing.

This bug was not present in 3.0, but this patch is cc'd to
stable because adf92eab90e3f5f34c285 where the bug was
introduced was marked for stable.

Fixes: adf92eab90e3f5f34c285
Cc: qemu-stable@nongnu.org (3.0.1)
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>