drm/ttm: Allocate the page pool manager in the heap.

Repeated ttm_page_alloc_init/fini fails noisily because the pool
manager kobj isn't zeroed out between uses (we could do just that but
statically allocated kobjects are generally considered a bad thing).
Move it to kzalloc'ed memory.

Note that this patch drops the refcounting behavior of the pool
allocator init/fini functions: it would have led to a race condition
in its current form, and anyway it was never exploited.

This fixes a regression with reloading kms modules at runtime, since
page allocator was introduced.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

include/drm/ttm/ttm_page_alloc.h

@@ -56,10 +56,6 @@ void ttm_put_pages(struct list_head *pages,
 		   enum ttm_caching_state cstate);
 /**
  * Initialize pool allocator.
- *
- * Pool allocator is internaly reference counted so it can be initialized
- * multiple times but ttm_page_alloc_fini has to be called same number of
- * times.
  */
 int ttm_page_alloc_init(struct ttm_mem_global *glob, unsigned max_pages);
 /**