In preparation for garbage collecting dynamically allocated EFI memory
maps, where the allocation method of memblock vs slab needs to be
recalled, convert the existing 'late' flag into a 'flags' bitmask.

Arrange for the flag to be passed via 'struct efi_memory_map_data'. This
structure grows additional flags in follow-on changes.
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Signed-off-by: NIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200113172245.27925-11-ardb@kernel.org