wifi: wfx: implement wfx_remain_on_channel()

With some conditions, the device is able to send/receive frames during
scan operation. So, it is possible to use it implement the "remain on
channel" feature. We just ask for a passive scan (without sending any
probe request) on one channel.

This architecture allows to leverage some interesting features:
- if the device is AP, the device switches channel just after the next
beacon and the beacons are stopped during the off-channel interval.
- if the device is connected, it advertises it is asleep before to
switch channel (so the AP should stop to try to send data)

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231004172843.195332-9-jerome.pouiller@silabs.com

wifi: wfx: scan_lock is global to the device

Currently, one scan_lock is associated to each vif. However, concurrent
scan on vifs is explicitly prohibited by the device. Currently,
scan_lock is associated with a vif but it is always locked with
conf_mutex (there is a case where conf_mutex is not associated to
scan_lock but scan_lock is tested on all interfaces). So concurrent scan
on vifs cannot happen.

So, this patch relocate scan_lock to the device and simplify the code.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231004172843.195332-7-jerome.pouiller@silabs.com

wfx: use container_of() to get vif

Currently, upon virtual interface creation, wfx_add_interface() stores
a reference to the corresponding struct ieee80211_vif in private data,
for later usage. This is not needed when using the container_of
construct. This construct already has all the info it needs to retrieve
the reference to the corresponding struct from the offset that is
already available, inherent in container_of(), between its type and
member inputs (struct ieee80211_vif and drv_priv, respectively).
Remove vif (which was previously storing the reference to the struct
ieee80211_vif) from the struct wfx_vif, define a function
wvif_to_vif(wvif) for container_of(), and replace all wvif->vif with
the newly defined container_of construct.

Signed-off-by: Jaehee Park <jhpark1013@gmail.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220506170046.GA1297231@jaehee-ThinkPad-X1-Extreme

wfx: get out from the staging area

The wfx driver is now mature enough to leave the staging area.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>