Make multi-part AEAD operations thread-safe

The setup calls are the only calls to use a key ID.
The key is then copied into the operation object,
all future API calls use the copy instead of the key in the slot.

Simultaneous API calls on the same operation object are not thread-safe.

Signed-off-by: Ryan Everett <ryan.everett@arm.com>

library/psa_crypto.c

@@ -4687,7 +4687,7 @@ static psa_status_t psa_aead_setup(psa_aead_operation_t *operation,
     operation->key_type = psa_get_key_type(&attributes);
 
 exit:
-    unlock_status = psa_unregister_read(slot);
+    unlock_status = psa_unregister_read_under_mutex(slot);
 
     if (status == PSA_SUCCESS) {
         status = unlock_status;