tests/boards: Add intel_adsp board integration/smoke test

As Zephyr begins to absorb drivers for these platforms that had
previously been managed by the SOF app, there's a need for a rapid
board-specific smoke test to use during development.

This starts with the smp_boot_delay test (itself a unit test for a
SOF-derived feature) and adds a host IPC case (that needs to match
code in cavstool.py on the other side of the PCI bus!).

It will grow more features over time as needed.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>