rt2x00: Simplify Queue function arguments

A lot of functions accept a struct rt2x00_dev combined with
either a struct queue_entry or struct data_queue argument.
This can be simplified by only passing on the queue/entry
argument.

In cases where rt2x00_dev and a sk_buff are send together,
we can send the queue_entry instead.

rt2x00usb_alloc_urb and rt2x00usb_free_urb have a bit
of vague naming. Instead they allocate all the data which
belongs to a rt2x00 data queue entry.

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