gallium: Fix u_stream_outputs_for_vertices with QUADS

gallium: Fix u_stream_outputs_for_vertices with QUADS

Per the spec. This helper is only used in nv50 and panfrost, the latter is known
to have a completely broken transform feedback implementation and I'd be
unsurprised if the same is true for nv50. So unsurprising that compatibility
profile interaction was missed.

This is part of the Piglit ext_transform_feedback-tessellation quads puzzle.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Acked-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22013>