drm/vmwgfx: Don't refcount cotable lookups during command buffer validation

The typical pattern of these lookups are
-Lookup
-Put on validate list if not already there.
-Unreference
And since we are the exclusive user of the context during lookup time,
we can be sure that the resource will stay alive during the sequence.
So avoid taking a reference during lookup, and also avoid unreferencing
when done. There are two users outside of command buffer validation and
those are refcounted explicitly.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_context.c

@@ -861,9 +861,8 @@ struct vmw_resource *vmw_context_cotable(struct vmw_resource *ctx,
 	if (cotable_type >= SVGA_COTABLE_DX10_MAX)
 		return ERR_PTR(-EINVAL);
 
-	return vmw_resource_reference
-		(container_of(ctx, struct vmw_user_context, res)->
-		 cotables[cotable_type]);
+	return container_of(ctx, struct vmw_user_context, res)->
+		cotables[cotable_type];
 }
 
 /**