wifi: rtw89: wow: implement PS mode for net-detect

When net-detect is enabled, WoWLAN firmware will periodically
scan until beacon or probe response of configured networks are
received. To reduce power consumption, the FW-IPS mode is
implemented to keep WiFi chip in idle mode between each scan.
The FW-IPS is controlled by WoWLAN firmware to turn of some critical
electrical components, and is different from the original IPS mode
which most electrical components are turned off.

Signed-off-by: Chin-Yen Lee <timlee@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20240805090028.27768-3-pkshih@realtek.com