Add Energy Detected CCA (EDCCA) mechanism to detect energy on the channel.
And EDCCA support adaptivity mode now. From MIC Ordinance Regulating Radio
Equipment article 49.20, ETSI EN-300-328 and EN-301-893, the device should
be able to dynamically pause TX activity when energy detected on the air.
According to ETSI/JP DFS region, driver will set corresponding threshold
and stop TX activity if the detected energy exceeds the threshold. For now,
we support it on 8822b and 8822c first.

By default, EDCCA mechanism is turned on. For ETSI/JP DFS region, it will
turn to adaptivity mode. However, with adaptivity, if environment is too
noisy, TX may often be halted. So, a debugfs for EDCCA is added. It can
show what EDCCA mode is used currently. And EDCCA mechanism can be turned
on/off through the debugfs while debugging.
Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210830072014.12250-4-pkshih@realtek.com