rt2x00: Rename txentry_desc.queue -> txentry_desc.qid

Variables containing queue ids are called qid everywhere else, hence
rename the queue field in txentry_desc to qid as well.

Signed-off-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>