[Flang][OpenMP] Minor cosmetic changes post-PR#77758, NFC

Rename `getCollapsedEval` to `getCollapsedLoopEval`, and move condition
check from `getCollapsedLoopEval` to `genNestedEvaluations` (the only
caller).

Author: kparzysz

flang/lib/Lower/OpenMP.cpp

@@ -111,9 +111,8 @@ static void gatherFuncAndVarSyms(
 }
 
 static Fortran::lower::pft::Evaluation *
-getCollapsedEval(Fortran::lower::pft::Evaluation &eval, int collapseValue) {
-  // Return the Evaluation of the innermost collapsed loop, or the current
-  // evaluation, if there is nothing to collapse.
+getCollapsedLoopEval(Fortran::lower::pft::Evaluation &eval, int collapseValue) {
+  // Return the Evaluation of the innermost collapsed loop.
   if (collapseValue == 0)
     return &eval;
 
@@ -132,7 +131,7 @@ static void genNestedEvaluations(Fortran::lower::AbstractConverter &converter,
                                  Fortran::lower::pft::Evaluation &eval,
                                  int collapseValue = 0) {
   Fortran::lower::pft::Evaluation *curEval =
-      getCollapsedEval(eval, collapseValue);
+      collapseValue == 0 ? &eval : getCollapsedLoopEval(eval, collapseValue);
 
   for (Fortran::lower::pft::Evaluation &e : curEval->getNestedEvaluations())
     converter.genEval(e);