[usbdev/dif] Add the rest of the unit tests
[usbdev/dif] Add the rest of the unit tests

Add unit tests for IN packets, observing status, controlling the device
address, interacting with the AON wake module, and setting up the TX
test mode.

Signed-off-by: Alexander Williams <d0fb8a15e7b6f5e62278a4cf44515038c232186c@google.com>

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