rtw89: support variant of fill_txdesc

The txdesc is descriptor related to skb->data. The v1 version contains
8 dwords txwd_body and 6 dwords txwd_info, and the format is also different
from original one.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220318023214.32411-10-pkshih@realtek.com