KEYS: trusted: dcp: fix NULL dereference in AEAD crypto operation

In the Linux kernel, the following vulnerability has been resolved: KEYS: trusted: dcp: fix NULL dereference in AEAD crypto operation When sealing or unsealing a key blob we currently do not wait for the AEAD cipher operation to finish and simply return after submitting the request. If there is some load on the system we can exit before the cipher operation is done and the buffer we read from/write to is already removed from the stack. This will e.g. result in NULL pointer dereference errors in the DCP driver during blob creation. Fix this by waiting for the AEAD cipher operation to finish before resuming the seal and unseal calls.