BUG: sparse: The dtype argument to the dok_matrix constructor was not handled correctly when the input data was a list of lists.

Example of the issue:

    In [1]: from scipy.sparse import dok_matrix
    
    In [2]: d = dok_matrix([[0, 1, 2], [3, 0, 0]], dtype=np.float32)
    
    In [3]: d.dtype
    Out[3]: dtype('int64')

The result in `Out[3]` should be 'float32'.