liboverlay: remove warnings during compilation

- Remove unused variables
- Use proper typecast

Change-Id: Ia60fc4c3c7ec39a1df4a780de7f5d75d723f7960
diff --git a/liboverlay/overlayMdpRot.cpp b/liboverlay/overlayMdpRot.cpp
index ce2ef5b..3e549b1 100755
--- a/liboverlay/overlayMdpRot.cpp
+++ b/liboverlay/overlayMdpRot.cpp
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2008 The Android Open Source Project
- * Copyright (c) 2010-2013, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2010-2014, The Linux Foundation. All rights reserved.
  * Not a Contribution, Apache license notifications and license are retained
  * for attribution purposes only.
  *
@@ -94,7 +94,7 @@
     mRotImgInfo.dst.height = whf.h;
 }
 
-void MdpRot::setCrop(const utils::Dim& crop) {
+void MdpRot::setCrop(const utils::Dim& /*crop*/) {
     // NO-OP for non-mdss rotator due to possible h/w limitations
 }