mm/sparse: move buffer init/fini to the common place

mm/sparse: move buffer init/fini to the common place

Now that both variants of sparse memory use the same buffers to populate
memory map, we can move sparse_buffer_init()/sparse_buffer_fini() to the
common place.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Pavel Tatashin <[email protected]>
Tested-by: Michael Ellerman <[email protected]>	[powerpc]
Tested-by: Oscar Salvador <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Pasha Tatashin <[email protected]>
Cc: Abdul Haleem <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Daniel Jordan <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jérôme Glisse <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Souptick Joarder <[email protected]>
Cc: Steven Sistare <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Wei Yang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>