Add CI-based module build

I built native ARM64 and using binary kernel. This will enable you to do faster cycles by replicating the build on BeaglePlay itself.

The docker image build is at https://git.beagleboard.org/jkridner/kernel-build-env

The limitation is this build process will need to be modified to test against the mainline kernel, but without modifying any of the rest of the kernel, this should be reasonable.