Revert "arm64: Use level-2 for largest block mappings when FEAT_HAFDBS is present"

This reverts commit 836b8d4b. This is
part of a series trying to make use of the arm64 hardware features for
tracking dirty pages. Unfortunately this series causes problems for the
AC5/AC5X SoCs. Having exhausted other options the consensus seems to be
reverting this series is the best course of action.

Signed-off-by: Chris Packham <judge.packham@gmail.com>