Support for encrypted off-chip BL

[RobertBuhren]

When an uefi image is used with an encrypted off-chip BL, the current ccpv5 emulation will decrypt the off-chip using an un-initialized CCP LSB context as the key.

IMHO it would be better to detect such cased (if possible) and warn the user that the decryption output is useless.

The long-term solution is to retrieve the initial seed for the CCP LSB's so the emulator can successfully decrypt the off-chip BL.