dri: Remove driRenderbuffer::backBuffer field

The tdfx driver was the only user.

Acked-by: Kristian Høgsberg <krh@bitplanet.net>
Acked-by: Marek Olšák <maraeo@gmail.com>
Acked-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Acked-by: Jakob Bornecrantz <jakob@vmware.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Build-Tested-by: Jakob Bornecrantz <jakob@vmware.com>
Tested-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
1 file changed