Add unit test for the GHOST_IOC_SW_GET_INFO ioctl.
Add unit test for the GHOST_IOC_SW_GET_INFO ioctl.

Specifically we verify that we can retrieve status words for every
agent cpu and also that invalid cpus fail with an errno of EINVAL.

google/ghost-userspace,google/ghost-userspace,google/ghost-userspace,google/ghost-userspace