iwlwifi patches for 4.20
* One fix for channel-switch handling;
* Some improvements in the HE code;
* New FW API handling;
* Improvements in the debugging code;
* Some improvements in the PCI recovery mechanism;
* Support for a few FW API changes;
* Enable a new scanning feature;
* Continued work on HE (mostly radiotap);
* Some fixes in the FW rate-scaling implementation;
* Other clean-ups and small fixes and improvements;