Make the DECT-2020 NR+ libmodem.a available as well

[chrysn]

A part of libmodem is the DECT PHY interface; this PR includes the library.

The DECT part is currently hard to test because the radio core firmware is only available on request; while the nascent hophop docs describe how to flash it, "you must contact the Nordic Semiconductor sales department" to get the actual zip file.

I yet have to assemble an application with which this could be tested by those who have the firmware image, hence the "draft" status. Until then, questions to discuss are:

• Do we expect more libraries to require the cleanup step? (Then what is now code copy-paste could become a loop.)
• Would this be an acceptable pull request before the DECT firmware is made available to the general public, or devkits can be bought that have it flashed off the shelf?

[diondokter]

Do we expect more libraries to require the cleanup step? (Then what is now code copy-paste could become a loop.)

Unless you've got your sights onto something, I think not? The PR looks good.

Would this be an acceptable pull request before the DECT firmware is made available to the general public, or devkits can be bought that have it flashed off the shelf?

I would be hesitant to make a release for it. Merge it into main? Maybe. But a release really has to be tested.

This repo doesn't see a whole lot of updates, so an open PR won't bitrot very fast.
But I can image it's very annoying if you need to use git deps all the time. (And also, it'd prevent you from releasing dependents on crates.io too)

Do you know when the modem firmware comes generally available? The docs already have been for a while...

[chrysn]

Closing in favor of #16; this one is based on misinterpreted linker errors.