freedreno/a6xx: Pre-bake SO-disable stateobj

freedreno/a6xx: Pre-bake SO-disable stateobj

No need to re-create this every time we transition from stream-out
enabled to disabled.

Creation of streamout_disable_stateobj is deferred until we create
a program state using streamout to avoid creating it unnecessarily
and because fd6_prog_init() is called before ctx->pipe is created.
(Changing that ordering is complicated by the fact that u_blitter
copies pctx->bind_fs_state(), and friends.)

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12918>