[OMPIRBuilder] Avoid use of getPointerElementType()

Looks like I missed this call when removing others in this file.

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

@@ -3451,7 +3451,7 @@ OpenMPIRBuilder::InsertPointTy OpenMPIRBuilder::createAtomicCapture(
     Type *XTy = X.Var->getType();
     assert(XTy->isPointerTy() &&
            "OMP Atomic expects a pointer to target memory");
-    Type *XElemTy = XTy->getPointerElementType();
+    Type *XElemTy = X.ElemTy;
     assert((XElemTy->isFloatingPointTy() || XElemTy->isIntegerTy() ||
             XElemTy->isPointerTy()) &&
            "OMP atomic capture expected a scalar type");