Set CWmax/CWmin, TXOP and AIFS according to ieee80211_tx_queue_params.

Do note that hardware has only one group of EDCA[ac] registers, if more
than one vif are added, the EDCA[ac] registers will contain value of
params of the most recent set by ieee80211_ops::conf_tx().

And AIFS = AIFSN[ac] * slot_time + SIFS, so if use_short_slot is changed,
need to also change AIFS.
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>