hw/aes.py: Fix python error after 183991c

Fixes: 183991c ("m1n1.hw.dart: Hide all DART variants behind common interface")
Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>

proxyclient/m1n1/hw/aes.py

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: MIT
 from ..utils import *
 from enum import IntEnum
-from .dart import DART, DARTRegs
+from .dart import DART
 import struct
 from enum import IntEnum