m68k/mm: use __ClearPageReserved()

The PG_reserved flag is cleared from memory that is part of the kernel
image (and therefore marked as PG_reserved).  Avoid using PG_reserved
directly.

Link: http://lkml.kernel.org/r/20190114125903.24845-6-david@redhat.com


Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>