Clarify expected response when "state" is incorrect for Verification event

[FragLegs]

In section 7.1.4.1, the SSF spec says that if the Receiver requests a Verification event with a state value and the Transmitter sends an incorrect state in the subsequent Verification event, the Receiver should respond with "setData".

Upon receiving a Verification event, the Event Receiver SHALL parse the SET and validate its claims. In particular, the Event Receiver SHALL confirm that the value for "state" is as expected. If the value of "state" does not match, an error response of "setData" SHOULD be returned (see Section 2.3 of {{RFC8935}} or {{RFC8936}}).

It is unclear what is being referenced and how exactly the Receiver should respond. We should add further clarification.

[tulshi]

Define a new registry entry for section 7.1 of RFC8935 and include that in the IANA considerations of this spec.