[lanai] Small cleanup: remove/comment out unused args

llvm-svn: 275636
diff --git a/llvm/lib/Target/Lanai/LanaiTargetMachine.h b/llvm/lib/Target/Lanai/LanaiTargetMachine.h
index 1f61608..5278c70 100644
--- a/llvm/lib/Target/Lanai/LanaiTargetMachine.h
+++ b/llvm/lib/Target/Lanai/LanaiTargetMachine.h
@@ -37,7 +37,7 @@
                      CodeModel::Model CodeModel, CodeGenOpt::Level OptLevel);
 
   const LanaiSubtarget *
-  getSubtargetImpl(const llvm::Function &Fn) const override {
+  getSubtargetImpl(const llvm::Function & /*Fn*/) const override {
     return &Subtarget;
   }