isSupportedReduction: simplify code

Author: Sven Verdoolaege

tc/core/polyhedral/reduction_matcher.cc

@@ -39,11 +39,8 @@ namespace {
 bool isSupportedReduction(Halide::Internal::Stmt stmt) {
   auto provide = stmt.as<Halide::Internal::Provide>();
   auto call = provide->values[0].as<Halide::Internal::Call>();
-  if (call && call->args.size() > 0 &&
-      call->args[0].as<Halide::Internal::Add>()) {
-    return true;
-  }
-  return false;
+  return call && call->args.size() > 0 &&
+      call->args[0].as<Halide::Internal::Add>();
 }
 
 // TODO: the function currently available in Scop only works _after_ inserting