wifi: rtw89: add RNR support for 6 GHz scan

Since 6 GHz band has around 60 channels and more strict rules for
active probing. Reduced neighbor report can be used to reduce the
channels we scan and get specific target BSS info to probe for.

Declare flag WIPHY_FLAG_SPLIT_SCAN_6GHZ so the scan request could be
divided into two portions: legacy bands and 6 GHz bands. So RNR
information from legacy bands could later be used when 6 GHz scan.

When the scan flag NL80211_SCAN_FLAG_COLOCATED_6GHZ is set, cfg80211
will pass down a reduced channel set which contains PSCs and non-PSC
with RNR info received in the 2 GHz/5 GHz band. This reduces the
scan duration by allowing us to only scan for channels in which APs
are currently operating.

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/20230217120007.8835-1-pkshih@realtek.com