travis: Add arm64 CI tests
travis: Add arm64 CI tests

Signed-off-by: Geoff Levand <c3918f39022407dee6a0056ceca9b1aa80e8e4ce@infradead.org>

travis-ci/gimme,glevand/travis-ci--gimme,meatballhat/gimme,travis-ci/gimme,glevand/travis-ci--gimme,kofalt/gimme