rtw88: fix incorrect frequency reported

We should only fill in frequency reported by firmware during scan.
Add this so frames won't 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/20220407095858.46807-3-pkshih@realtek.com