wifi: rtl8xxxu: Fix AIFS written to REG_EDCA_*_PARAM

ieee80211_tx_queue_params.aifs is not supposed to be written directly
to the REG_EDCA_*_PARAM registers. Instead process it like the vendor
drivers do. It's kinda hacky but it works.

This change boosts the download speed and makes it more stable.

Tested with RTL8188FU but all the other supported chips should also
benefit.

Fixes: 26f1fad2 ("New driver: rtl8xxxu (mac80211)")
Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Acked-by: Jes Sorensen <jes@trained-monkey.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/038cc03f-3567-77ba-a7bd-c4930e3b2fad@gmail.com