llvmpipe: pass stream-out targets to draw-module early

llvmpipe: pass stream-out targets to draw-module early

We currently set this state in the draw-module twice on each draw, but
which trashes this state. So far that's not a problem, because we don't
really do much from that function.

But it turns out, we're going to have to do more; namely flush when the
state changes. This will incur a large performance penalty due to the
excessive setting.

Instead, let's rely on the CSO caching making sure that
llvmpipe_set_so_targets doesn't get called needlessly, and setup the
state directly there instead.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>