[flang][OpenMP] Remove no longer used OmpLoopDirective, NFC (#159576)

Author: kparzysz

flang/examples/FeatureList/FeatureList.cpp

@@ -485,7 +485,6 @@ struct NodeVisitor {
   READ_FEATURE(OmpLinearClause::Modifier)
   READ_FEATURE(OmpLinearModifier)
   READ_FEATURE(OmpLinearModifier::Value)
-  READ_FEATURE(OmpLoopDirective)
   READ_FEATURE(OmpMapClause)
   READ_FEATURE(OmpMapClause::Modifier)
   READ_FEATURE(OmpNumTasksClause)

flang/include/flang/Parser/dump-parse-tree.h

@@ -615,7 +615,6 @@ class ParseTreeDumper {
   NODE_ENUM(OmpLinearModifier, Value)
   NODE(parser, OmpLocator)
   NODE(parser, OmpLocatorList)
-  NODE(parser, OmpLoopDirective)
   NODE(parser, OmpMapClause)
   NODE(OmpMapClause, Modifier)
   NODE(parser, OmpMapper)

flang/include/flang/Parser/parse-tree.h

@@ -5075,12 +5075,6 @@ struct OpenMPAtomicConstruct : public OmpBlockConstruct {
   mutable Analysis analysis;
 };
 
-// OpenMP directives that associate with loop(s)
-struct OmpLoopDirective {
-  WRAPPER_CLASS_BOILERPLATE(OmpLoopDirective, llvm::omp::Directive);
-  CharBlock source;
-};
-
 // 2.14.2 cancellation-point -> CANCELLATION POINT construct-type-clause
 struct OpenMPCancellationPointConstruct {
   WRAPPER_CLASS_BOILERPLATE(

flang/lib/Semantics/check-omp-structure.cpp

@@ -679,10 +679,6 @@ template <typename Checker> struct DirectiveSpellingVisitor {
     checker_(x.DirName().source, x.DirId());
     return false;
   }
-  bool Pre(const parser::OmpLoopDirective &x) {
-    checker_(x.source, x.v);
-    return false;
-  }
 
   bool Pre(const parser::OmpDirectiveSpecification &x) {
     auto &name = std::get<parser::OmpDirectiveName>(x.t);