Warn user about bad AES when TOTP is set up

[alex-nitrokey]

• Application version: 4.0
• Operating system: all
• Device model and firmware version: Storage 0.54
• Issue occurrency: always

Expected behaviour

If a user creates a TOTP she/he should get warned about broken AES key, like it is the case when encrypted volume is opened (see error message discussed here #264).

Current behaviour

The user is not warned about bad AES key so that she/he may set up the whole device including TOTP keys and only realizes the necessity of hitting "destroy encrypted data" button afterwards and thus needs to set up TOTP keys again.

[szszszsz]

AFAIR the AES key should be generated on the EV/PWS setup automatically, but will check that.

• [ ] make sure the AES key is generated, and device is initialized, before TOTP use

[szszszsz]

Closing as wontfix for now, as OTP flash space is not encrypted at the moment, thus AES key is not required. This might change in the future.