wifi: rtw89: fix wrong bandwidth settings after scan

Set channel in driver side to configure Tx power and channel index
correctly after scan. Before this, beacons with bandwidth larger than
20M bandwidth will be dropped by mac80211 due to frequency mismatch.

Signed-off-by: Po-Hao Huang <phhuang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221007045900.10823-2-pkshih@realtek.com