radv: stop overallocating LDS for VS/TES when NGG streamout is enabled

radv: stop overallocating LDS for VS/TES when NGG streamout is enabled

The number of shader outputs should only be considered when the
shader has XFB, otherwise we are overallocating LDS.

fossils-db (GFX1100):
Totals from 16602 (12.31% of 134913) affected shaders:
LDS: 17000448 -> 8500224 (-50.00%)

Cc: 22.3 mesa-stable
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19801>
(cherry picked from commit 499abeba605da7f7395c84b0a75c917656c19949)