ethtool: fix a build warning am: 63205d83b8 am: ce9e8b60ce am: 51bd9e9ff6

Original change: https://android-review.googlesource.com/c/platform/external/ethtool/+/2804535

Change-Id: I14fea5fc26128563248994927b7cf99fafc1e3ac
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>