driver: import missing drivers in __init__.py

It should be possible to specify the DeditecRelaisDriver and
USBTMCDriver in a labgrid environment config.

Signed-off-by: Bastian Krause <bst@pengutronix.de>

Author: Bastian-Krause

labgrid/driver/__init__.py

@@ -39,3 +39,5 @@
 from .provider import TFTPProviderDriver
 from .mqtt import TasmotaPowerDriver
 from .manualswitchdriver import ManualSwitchDriver
+from .usbtmcdriver import USBTMCDriver
+from .deditecrelaisdriver import DeditecRelaisDriver