mm: Convert all PageMovable users to movable_operations

These drivers are rather uncomfortably hammered into the
address_space_operations hole.  They aren't filesystems and don't behave
like filesystems.  They just need their own movable_operations structure,
which we can point to directly from page->mapping.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>