[OpenMP][NFCI] Use the libFrontend ProcBindKind in Clang

This removes the OpenMPProcBindClauseKind enum in favor of
llvm::omp::ProcBindKind which lives in OpenMPConstants.h and was
introduced in D70109.

No change in behavior is expected.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D70289
diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
index e59f964..9597eaa 100644
--- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
+++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
@@ -271,7 +271,7 @@
         getOrCreateRuntimeFunction(OMPRTL___kmpc_push_num_threads), Args);
   }
 
-  if (ProcBind != OMP_PB_default) {
+  if (ProcBind != OMP_PROC_BIND_default) {
     // Build call __kmpc_push_proc_bind(&Ident, global_tid, proc_bind)
     Value *Args[] = {
         Ident, ThreadID,