fix: add missing FP threshold in second ColorGraph call site

The loop-exit ColorGraph calls at line 1102-1103 were missing the
caller_saved_threshold parameter, causing FP to use default 19 instead
of correct 16.

src/mir/RegAlloc.cpp

@@ -1099,8 +1099,8 @@ namespace mir
       InterferenceGraph gp_graph, fp_graph;
       BuildInterferenceForGP(function, block_liveness, gp_alloc, gp_graph);
       BuildInterferenceForFP(function, block_liveness, fp_alloc, fp_graph);
-      auto gp_result = ColorGraph(gp_graph, gp_alloc, function);
-      auto fp_result = ColorGraph(fp_graph, fp_alloc, function);
+      auto gp_result = ColorGraph(gp_graph, gp_alloc, function, 19);
+      auto fp_result = ColorGraph(fp_graph, fp_alloc, function, 16);
       std::set<int> all_spilled = gp_result.spilled;
       for (int v : fp_result.spilled)
         all_spilled.insert(v);