wifi: rtw88: prohibit enter IPS during HW scan

Mac80211 core may ask driver to change to idle mode during HW scan,
then H2C command for HW scan will send failed since chip is in idle
mode. Therefore, We check the SCANNING flag before entering IPS to
prevent this behavior.

Signed-off-by: Chih-Kang Chang <gary.chang@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/20220809084107.38137-8-pkshih@realtek.com