OvmfPkg/PlatformPei: extract memory type info defaults to PCDs

OvmfPkg/PlatformPei: extract memory type info defaults to PCDs

Some OvmfPkg modules already depend on "EmbeddedPkg.dec"; thus, replace
the open-coded memory type info defaults in the source code with the
EmbeddedPkg PCDs that stand for the same purpose. Consequently, platform
builders can override these values with the "--pcd" option of "build",
without source code updates.

While at it, sort the memory type names alphabetically.

Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2706
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200508121651.16045-4-lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@arm.com>