lavapipe: fixup device allocate + enable private data

I'd only half ported private memory support, finish the job.

Cc: "20.3" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7705>
(cherry picked from commit 0d90c7cbc4d005fe6245d0a19985784940792403)
11 files changed