don't check version when not needed

theano/sandbox/cuda/dnn.py

@@ -2388,12 +2388,8 @@ if True:
               isinstance(node.inputs[0].owner.op, HostFromGpu)) or
              (node.inputs[1].owner and
                  isinstance(node.inputs[1].owner.op, HostFromGpu)))):
-            v = version()
-            if v[0] != v[1]:
-                return
             if not dnn_available():
                 # Softmax grad is broken in v3 rc1 for this case
-                # But we don't support cudnn v3 rc version now.
                 return
             ins = []
             for n in node.inputs: