wifi: ath10k: Use IEEE80211_SEQ_TO_SN() for seq_ctrl conversion

Use IEEE80211_SEQ_TO_SN() macro to convert seq_ctrl to sn for better
readability.

Signed-off-by: Zhi-Jun You <hujy652@gmail.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20221106162227.1119-1-hujy652@gmail.com