mm: cma: WARN if freed memory is still in use

mm: cma: WARN if freed memory is still in use

Memory returned to free_contig_range() must have no other references.
Let kernel to complain loudly if page reference count is not equal to 1.

[[email protected]: support sparsemem]
Signed-off-by: Marek Szyprowski <[email protected]>
Reviewed-by: Kyungmin Park <[email protected]>
Acked-by: Michal Nazarewicz <[email protected]>
Signed-off-by: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>