update_engine: Fix TPM variable name max_kernel_rollfoward

- In a previous CL I named the variable incorrectly

BUG=chromium:814090
TEST=FEATURES=test emerge-samus update_engine

Change-Id: I17cbc85d42ba03040bfdae436cedd0238698b47e
Reviewed-on: https://chromium-review.googlesource.com/1059944
Commit-Ready: Zentaro Kavanagh <zentaro@chromium.org>
Tested-by: Zentaro Kavanagh <zentaro@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/hardware_android.h b/hardware_android.h
index 4d354ac..a6c9f6a 100644
--- a/hardware_android.h
+++ b/hardware_android.h
@@ -44,7 +44,7 @@
   std::string GetECVersion() const override;
   int GetMinKernelKeyVersion() const override;
   int GetMinFirmwareKeyVersion() const override;
-  bool SetMaxKernelKeyRollforward(int max_kernel_rollforward) override;
+  bool SetMaxKernelKeyRollforward(int kernel_max_rollforward) override;
   int GetPowerwashCount() const override;
   bool SchedulePowerwash() override;
   bool CancelPowerwash() override;