rt2x00: remove data_queue_desc struct

If the queue_init callback is implemented
by a driver it gets used instead of the
data_queue_desc based initialization.

The queue_init callback is implemented for
each drivers now, so the old initialization
method is not used anymore. Remove the unused
data_queue_desc structure and all of the
related code.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>