Ensure kern_shape has `dtype` attribute.

theano/gpuarray/dnn.py

@@ -385,6 +385,7 @@ class GpuDnnConvDesc(COp):
         self.precision = precision
 
     def make_node(self, kern_shape):
+        kern_shape = as_tensor_variable(kern_shape)
         if kern_shape.type.ndim != 1 or kern_shape.dtype not in theano.tensor.basic.int_dtypes:
             raise TypeError('kern must be an int64 1D shape tensor')
         kern_shape = theano.tensor.basic.cast(kern_shape, 'int64')