lima/gpir: Ignore unscheduled successors in can_use_complex()

The point of the function is to avoid creating a complex move which is
used by certain slots in the next instruction, but unscheduled
successors will never be in the next instruction. Found while debugging
a crash that the previous commit fixed.

Reviewed-by: Vasily Khoruzhick <anarsoul@gmail.com>
Tested-by: Vasily Khoruzhick <anarsoul@gmail.com>

src/gallium/drivers/lima/ir/gp/scheduler.c

@@ -1154,7 +1154,8 @@ static bool can_use_complex(gpir_node *node)
          continue;
 
       gpir_node *succ = dep->succ;
-      if (succ->type != gpir_node_type_alu)
+      if (succ->type != gpir_node_type_alu ||
+          !succ->sched.instr)
          continue;
 
       /* Note: this must be consistent with gpir_codegen_{mul,add}_slot{0,1}