mac80211: introduce BSS color collision detection

Add ieee80211_rx_check_bss_color_collision routine in order to introduce
BSS color collision detection in mac80211 if it is not supported in HW/FW
(e.g. for mt7915 chipset).
Add IEEE80211_HW_DETECTS_COLOR_COLLISION flag to let the driver notify
BSS color collision detection is supported in HW/FW. Set this for ath11k
which apparently didn't need this code.

Tested-by: Peter Chiu <Chui-Hao.Chiu@mediatek.com>
Co-developed-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/a05eeeb1841a84560dc5aaec77894fcb69a54f27.1648204871.git.lorenzo@kernel.org
[clarify commit message a bit, move flag to mac80211]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>