OvmfPkg/AcpiPlatformDxe: prepare for QEMU_LOADER_WRITE_POINTER definitions

OvmfPkg/AcpiPlatformDxe: prepare for QEMU_LOADER_WRITE_POINTER definitions

No functional changes in this patch, just prepare the grounds with some
reformatting (trailing comma after the last enumeration constant,
horizontal whitespace insertion) so that the next patch can be cleaner.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=359
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>