common: also accept single digit values for mnclen

when using the --mnclen option it is easy to get confused with the
parameter. The parameter has to be a two digit hex value. To make things
easier lets convert a single digit hex value to two digit one
automatically.

common.py

@@ -84,6 +84,8 @@ class Common():
 			elif opt in ("-n", "--mnclen"):
 				self.show_mnclen = True
 			elif opt in ("-N", "--set-mnclen"):
+				if len(arg) == 1:
+					arg = "0" + arg
 				self.write_mnclen = asciihex_to_list(arg)
 			elif opt in ("-l", "--milenage"):
 				self.show_milenage = True