drm/vmwgfx: Update comments for stdu plane update

Update the comments to sync with code.

Signed-off-by: Deepak Rawat <drawat@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
1 file changed