ArmPkg/ArmMmuLib AARCH64: rewrite page table code

ArmPkg/ArmMmuLib AARCH64: rewrite page table code

Replace the slightly overcomplicated page table management code with
a simplified, recursive implementation that should be far easier to
reason about.

Note that, as a side effect, this extends the per-entry cache invalidation
that we do on page table entries to block and page entries, whereas the
previous change inadvertently only affected the creation of table entries.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Message-Id: <20200307083849.8940-2-ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>