rt2x00: Remove unused rt2x00queue_get_queue function.

Now that all accesses to the data_queue structures is done via the specialized
rt2x00queue_get_tx_queue function or via direct accesses, there is no
need for the rt2x00queue_get_queue function anymore, so remove it.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>