radv: Don't pass a TESS_EVAL shader when tesselation is not enabled.

radv: Don't pass a TESS_EVAL shader when tesselation is not enabled.

Otherwise on pre-GFX9, if the constant layout allows both TESS_EVAL and
GEOMETRY shaders, but the PIPELINE has only GEOMETRY, it would return the
GEOMETRY shader for the TESS_EVAL shader.

This would cause the flush_constants code to emit the GEOMETRY constants
to the TESS_EVAL registers and then conclude that it did not need to set
the GEOMETRY shader registers.

Fixes: dfff9fb6f8d "radv: Handle GFX9 merged shaders in radv_flush_constants()"
CC: 18.1 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Alex Smith <asmith@feralinteractive.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>