mm: move most of core MM initialization to mm/mm_init.c

mm: move most of core MM initialization to mm/mm_init.c

The bulk of memory management initialization code is spread all over
mm/page_alloc.c and makes navigating through page allocator functionality
difficult.

Move most of the functions marked __init and __meminit to mm/mm_init.c to
make it better localized and allow some more spare room before
mm/page_alloc.c reaches 10k lines.

No functional changes.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport (IBM) <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Doug Berger <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>