wifi: rtw89: wow: add scan interval option for net-detect

The scan interval option is the period in unit of second for WoWLAN
firmware to do each scan. We get the option from cfg80211 and practice it.
If the interval is too short for firmware to finish one scan, the firmware
will start next scan immediately after finishing one and the WiFi chip
could never enter idle mode to reduce power consumption.

Signed-off-by: Chin-Yen Lee <timlee@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20240826090439.17242-5-pkshih@realtek.com