r600/sb: Fall back to un-optimized shader if scheduling fails

Sometimes the optimizer created codes that can't be scheduled,
instead of failing completely, simply bail out and use the
un-optimized code.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16499>

src/gallium/drivers/r600/sb/sb_sched.cpp

@@ -1205,15 +1205,13 @@ bool post_scheduler::schedule_alu(container_node *c) {
 	if (!ready.empty()) {
 		sblog << "##post_scheduler: unscheduled ready instructions :";
 		dump::dump_op_list(&ready);
-		assert(!"unscheduled ready instructions");
 	}
 
 	if (!pending.empty()) {
 		sblog << "##post_scheduler: unscheduled pending instructions :";
 		dump::dump_op_list(&pending);
-		assert(!"unscheduled pending instructions");
 	}
-	return improving;
+	return pending.empty() && ready.empty() && improving != 0;
 }
 
 void post_scheduler::add_interferences(value *v, sb_bitset &rb, val_set &vs) {