LinuxKPI: 802.11: add support for suspend/resume

Add support for automatic suspend/resume as we know it for wireless.
The problem is that the PCI driver which would normally gets the code
is the Lin

LinuxKPI: 802.11: add support for suspend/resume

Add support for automatic suspend/resume as we know it for wireless.
The problem is that the PCI driver which would normally gets the code
is the LinuxKPI PCI framework/Linux wireless driver, which we cannot
ammend or generally add extra suspend/resume code to.
A further problem is that with growing support, the LinuxKPI 802.11
(mac80211) layer also is involved in suspend/resume for WoWLAN (not
yet supported) meaning that we need to hook the suspend/resume
framework into that as well. Unlike Linux we do not have a general
suspend/resume "hook" we can hang into and we need to tie this one
to the hardware so cannot indepedently (after the driver one) run it.

The solution for FreeBSD, in order to not mangle the Linux native
drivers and get extra maintanace overhead, is to add a bus child
which inherits the general framework and thus is 2 lines + #includes
for each driver extra to add to.

The general suspend/resume framework lives in LinuxKPI (linuxkpi_80211_pm)
and imitates the normal suspend/resume path overloading it (there is
a slight code/logic duplication from the PCI code).
Given we are passed the LinuxKPI p(ci)dev, we can go and peel out the
net80211 ic from the native bsddev and that way get access to the
wireless stack. We then call into LinuxKPI 802.11 in order to do
the suspend/resume dance there, and, if needed also call the
official suspend/resume routine from the device driver after
(reverse for resume).
If any in this fails, suspend will be blocked as we will return the
error (no different to any native driver could do).

The LinuxKPI 802.11 suspend/resume code has the initial code for
doing a WoWLAN suspend (one could change the sysctl) but other bits
like access to ifnet flags etc. has to be sorted out before we can
go and support that.
The default code path calles into net80211 to clear everything
like native wireless drivers do. The one thing we need to do in
addition is to remove the vif devices from the firmware and restore
them prior to net80211 resume.
We also check for a possible HW SCAN to still be runinng on resume
and warn as that may cause problems though the scan should be stopped
before suspend (we may still get a callback). You can easily see
these problems if you suspend/resume without stopping the wlan.

Enable the PM framework for iwlwifi in the module Makefile to
be able to use all this; others can follow as tested.

In case anyone has problems with this, they can change the sysctl
back to 0 until we can figure out any further problems.
The linuxkpi_wlan.4 man page got adjusted to document this.

Sponsored by: The FreeBSD Foundation
Tested on: Dell XPS 13 (AX200), Lenovo TP X270 (AX210)
MFC after: 3 days
PR: 263632

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