ArmPkg/ArmMmuLib: don't replace table entries with block entries

ArmPkg/ArmMmuLib: don't replace table entries with block entries

Drop the optimization that replaces table entries with block entries and
frees the page tables in the subhierarchy that is being replaced. This
rarely occurs in practice anyway, and will require more elaborate TLB
maintenance once we switch to a different approach where we no longer
disable the MMU and nuke the TLB entirely every time we update a
descriptor in a way that requires break-before-make (BBM).

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>