arm64: Implement pmdp_set_access_flags() for hardware AF/DBM

The update to the accessed or dirty states for block mappings must be
done atomically on hardware with support for automatic AF/DBM. The
ptep_set_access_flags() function has been fixed as part of commit
66dbd6e6 ("arm64: Implement ptep_set_access_flags() for hardware
AF/DBM"). This patch brings pmdp_set_access_flags() in line with the pte
counterpart.

Fixes: 2f4b829c ("arm64: Add support for hardware updates of the access and dirty pte bits")
Cc: <stable@vger.kernel.org> # 4.4.x: 66dbd6e6: arm64: Implement ptep_set_access_flags() for hardware AF/DBM
Cc: <stable@vger.kernel.org> # 4.3+
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>