MFC r313415:

[iwm] Implement apmg_wake_up_wa workaround properly for 7000 family.

* Add iwm_pcie_set_cmd_in_flight() and iwm_pcie_clear_cmd_in_flight()
helper methods.

* Use ring->queued tracking in the command queue to set/clear the
cmd_hold_nic_awake bit at the right points.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Import OpenBSD's iwm WiFi driver for Intel 3160/7260/7265.

There are still several bugs, but I've been using it for a while now.
Thanks to all the testers and to Adrian for his help with this
driver.

This driver isn't connected to the build yet, but it will be soon.

There's no MFC planned because the driver isn't very stable yet.

Reviewed by: adrian
Obtained from: https://github.com/rpaulo/iwm
Tested by: adrian, gjb, dumbbell (others that I forgot).
Relnotes: yes