Adjust the setup-qemu and test-qemu-hifive make actions to work with the new tock version.
Adjust the setup-qemu and test-qemu-hifive make actions to work with the new tock version.

PR #207 updated the tock submodule. The new submodule version includes the following PR: https://github.com/tock/tock/pull/1880, which changed the tock Makefile actions related to QEMU setup. This updates `make setup-qemu` to work with the new Tock makefile.

Tock no longer checks if QEMU was already setup when running setup actions, so I removed test-qemu-hifive's dependency on qemu-setup; users will need to run qemu-setup manually.

tock/libtock-rs