Ownership Transfer: ambiguity around ownership status during update-from-EEPROM flow

In the section of the ownership transfer documentation that discusses [transferring ownership via EEPROM update](https://github.com/lowRISC/opentitan/blob/master/doc/security/specs/ownership_transfer/_index.md#ownership-transfer), I see "The Device is initially in UNOWNED state" and "The current owner endorses the next owner keys" in close proximity to each other. This seems to imply that a chip has an owner while it is in the UNOWNED state.

The ["Unlock Ownership"](https://github.com/lowRISC/opentitan/blob/master/doc/security/specs/ownership_transfer/_index.md#unlock-ownership-unlock-ownership) section should make it clear that the chip retains its prior owner when it transitions to UNOWNED.

@moidx