mm: move page flags layout to separate header

mm: move page flags layout to separate header

This is a preparation patch for moving page->_last_nid into page->flags
that moves page flag layout information to a separate header.  This
patch is necessary because otherwise there would be a circular
dependency between mm_types.h and mm.h.

Signed-off-by: Mel Gorman <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Simon Jeons <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>