drm/vram: Have VRAM MM call GEM VRAM functions directly

VRAM MM and GEM VRAM buffer objects are only used with each other;
connected via 3 function pointers. Simplify this code by making the
memory manager call the rsp. functions of the BOs directly; and
remove the functions from the BO's public interface.

v2:
	* typos in commit message

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190911110910.30698-3-tzimmermann@suse.de

drivers/gpu/drm/ast/ast_ttm.c

@@ -41,7 +41,7 @@ int ast_mm_init(struct ast_private *ast)
 
 	vmm = drm_vram_helper_alloc_mm(
 		dev, pci_resource_start(dev->pdev, 0),
-		ast->vram_size, &drm_gem_vram_mm_funcs);
+		ast->vram_size);
 	if (IS_ERR(vmm)) {
 		ret = PTR_ERR(vmm);
 		DRM_ERROR("Error initializing VRAM MM; %d\n", ret);