rtw89: fix channel inconsistency during hw_scan

Previously channel maintained by driver could be different from the
ones hardware actually is. Restore these variables back to prevent
unexpected behavior.

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/20220520071731.38563-2-pkshih@realtek.com