Remove Connection.inputChannel

We are already storing InputChannel inside the InputPublisher. In
subsequent CLs, InputPublisher will be the only owner of InputChannel.

Bug: 161009324
Test: TEST=inputflinger_tests; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST
Change-Id: I47eac4a5aef564f3789ee8b90f7210fc04fd8d3a
3 files changed