ir3: make mark_kill_path exit early if instr is already seen

Would bring down its complexity in pathological cases.

Signed-off-by: Danylo Piliaiev <dpiliaiev@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9386>

src/freedreno/ir3/ir3_sched.c

@@ -871,6 +871,11 @@ static void
 mark_kill_path(struct ir3_instruction *instr)
 {
 	struct ir3_sched_node *n = instr->data;
+
+	if (n->kill_path) {
+		return;
+	}
+
 	n->kill_path = true;
 
 	foreach_ssa_src (src, instr) {