Until authenticated the platform enforces a state machine. Adjust
unit tests with this in mind.

Correct the return codes for all the states the unit tests ends up
hitting:

* Set Param / Get Param: DBC_ERROR_BAD_STATE
* Set UID: DBC_ERROR_SIGNATURE_INVALID
* Authencitated Nonce: DBC_ERROR_BAD_PARAMETERS
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>