target/arm: Adjust the order of Phys and Stage2 ARMMMUIdx

target/arm: Adjust the order of Phys and Stage2 ARMMMUIdx

It will be helpful to have ARMMMUIdx_Phys_* to be in the same
relative order as ARMSecuritySpace enumerators. This requires
the adjustment to the nstable check. While there, check for being
in secure state rather than rely on clearing the low bit making
no change to non-secure state.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230620124418.805717-8-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>