iwm: update if_iwmreg.h to the latest (as of today) openbsd changes

Summary:
This updates the if_iwmreg.h definitions to;

OpenBSD: if_iwmreg.h,v 1.65 2021/10/11 09:03:22 stsp Exp

A few things haven't been fully converted, namely:

• I left a couple things as enums for now just to reduce the other diffs needed; but they're the same values

• The IWM_SCD_QUEUE_* macros have different offsets which I didn't update in case they broke things / changed based on later firmware. But they also may be real bugfixes which are needed for later chips. It'll need more testing before flipping this on.

The c file updates are:

• Use the newer names for things if the name changed but the semantics didn't
• Explicitly use the earlier firmware structs which maintain compat with the current firmware and code. The newer ones are in here and they'll get converted when more openbsd code is merged into this tree.
• Use the older iwm rate table for now, which has entries for legacy rates, HT and VHT. Our code works with that right now, updating it to openbsd's err, "different" version can be done at a later date when HT/VHT support is added.

Notably, a bunch of definitions were deleted that weren't used.
They're not used either in the openbsd/dfbsd drivers so I think it's
safe to delete them in the long run.

Test Plan: 7260 hw 0x140

Subscribers: imp
Differential Revision: https://reviews.freebsd.org/D32627
Reviewed by: md5
Obtained From: OpenBSD