add new hal for double H bridge stepper motor driver

cnc/hal.py

@@ -98,7 +98,11 @@
 
 # check which module to import
 try:
-    from cnc.hal_raspberry.hal import *
+    from cnc.config import *
+    if ENABLE_L293D:
+        from cnc.hal_raspberry.hal2 import *
+    else:
+        from cnc.hal_raspberry.hal import *
 except ImportError:
     print("----- Hardware not detected, using virtual environment -----")
     print("----- Use M111 command to enable more detailed debug -----")