radv: fix passing clip/cull distances from VS to PS

CTS doesn't test input clip/cull distances for the fragment
shader stage, which explains why this was totally broken. I
wrote a simple test locally that works now.

This fixes a crash with GTA V and DXVK.

Note that we are exporting unused parameters from the vertex
shader now, but this can't be optimized easily because we don't
keep the fragment shader info...

Cc: mesa-stable@lists.freedesktop.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107477


Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
(cherry picked from commit 6f47df31)