drm/vmwgfx: Look up user buffer objects without taking a reference

Identically to how we look up ttm base objects witout reference, provide
the same functionality to vmw user buffer objects which derive from them.

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