Revert "armv8: enable HAFDBS for other ELx when FEAT_HAFDBS is present"

This reverts commit c1da6fdb. 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>