[turbofan] Rename {CheckPoint} to {Checkpoint} everywhere.

src/compiler/effect-control-linearizer.cc

Index: src/compiler/effect-control-linearizer.cc
diff --git a/src/compiler/effect-control-linearizer.cc b/src/compiler/effect-control-linearizer.cc
index 547f3da97d099706f2eec6ef450eb86537e025ec..2e597383ffc78f5adc3a5596a52630ca5b9f8156 100644
--- a/src/compiler/effect-control-linearizer.cc
+++ b/src/compiler/effect-control-linearizer.cc
@@ -293,9 +293,9 @@ void EffectControlLinearizer::ProcessNode(Node* node, Node** effect,
     return RemoveRegionNode(node);
   }
 
-  // Special treatment for CheckPoint nodes.
+  // Special treatment for checkpoint nodes.
   // TODO(epertoso): Pickup the current frame state.
-  if (node->opcode() == IrOpcode::kCheckPoint) {
+  if (node->opcode() == IrOpcode::kCheckpoint) {
     // Unlink the check point; effect uses will be updated to the incoming
     // effect that is passed.
     node->Kill();