rt2x00: Remove data_desc structure

Coverty indicated that data_desc with a single
element array is bad coding style. This removes
the structure and forces everybody to use __le32.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>