Revert reg-alloc change

Author: ChAoSUnItY

src/reg-alloc.c

@@ -320,13 +320,10 @@ void reg_alloc()
         if (fn->func->va_args) {
             for (int i = 0; i < MAX_PARAMS; i++) {
                 ph2_ir_t *ir = bb_add_ph2_ir(fn->bbs, OP_store);
-                // FIXME: Currently derefence issue caused by mixed subscription
-                // and arrow operators is fixed, but the original code is now
-                // causing problem, fixing it later.
-                var_t *param_def = &fn->func->param_defs[i];
 
                 if (i < fn->func->num_params)
-                    param_def->subscripts[0]->offset = fn->func->stack_size;
+                    fn->func->param_defs[i].subscripts[0]->offset =
+                        fn->func->stack_size;
 
                 ir->src0 = i;
                 ir->src1 = fn->func->stack_size;