mm/memory_hotplug.c: make register_mem_sect_under_node() a callback of walk_memory_ra...

mm/memory_hotplug.c: make register_mem_sect_under_node() a callback of walk_memory_range()

link_mem_sections() and walk_memory_range() share most of the code, so
we can use convert link_mem_sections() into a dummy function that calls
walk_memory_range() with a callback to register_mem_sect_under_node().

This patch converts register_mem_sect_under_node() in order to match a
walk_memory_range's callback, getting rid of the check_nid argument and
checking instead if the system is still boothing, since we only have to
check for the nid if the system is in such state.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Oscar Salvador <[email protected]>
Suggested-by: Pavel Tatashin <[email protected]>
Tested-by: Reza Arbab <[email protected]>
Tested-by: Jonathan Cameron <[email protected]>
Reviewed-by: Pavel Tatashin <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>