target/arm: Implement FEAT_HAFDBS, access flag portion

Perform the atomic update for hardware management of the access flag.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20221024051851.3074715-13-richard.henderson@linaro.org
[PMM: Fix accidental PROT_WRITE to PAGE_WRITE; add missing
 main-loop.h include]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
3 files changed