st/mesa: only set primitive_restart when the restart index is in range

Even when enabled, primitive restart has no effect when the restart index
is larger than the representable values in the index buffer.

Fixes GL45-CTS.gtf31.GL3Tests.primitive_restart.primitive_restart_upconvert
for radeonsi VI.

v2: add an explanatory comment

Cc: "12.0 13.0" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Marek Olšák <marek.olsak@amd.com> (v1)
1 file changed