Add USBFS register definitions

[i509VCB]

Will merge after embassy-usb-driver implementation is done.

[decaday]

Hi @i509VCB ,

I recently got an MSPM0G5187 development board and am looking to add USB support to embassy-mspm0. While looking into it, I found this PR.

I noticed the MSPM0 series uses the MUSB IP (mspm0g518x and g511x use the standard MUSB layout, while c511x uses a simplified one). I previously wrote a generic musb driver that implements embassy-usb-driver and has already been verified on MCUs from two other vendors.

I saw that this PR is waiting on the driver implementation to be done. Since this thread has been inactive for a while, I'd be very happy to pick this up.

Let me know if you are okay with this, or if you have any thoughts or context to share before I start!

[i509VCB]

I would like to share IP where possible. Happy to try that. Not sure how fucked up the MSPM0 implementation is going to be but I see 0 errata.

I also initially wrote this based of a prerelease reference manual, some prerelease metadata in sysconfig and guessing from the MSP432 peripheral.

[decaday]

Fortunately, it didn't take too much effort—it works and successfully enumerates!

I will clean up the code, polish the tests and open a PR. But I'm currently waiting for embassy-rs/embassy#6732 (or embassy-rs/embassy#6652) to be merged first. The breaking changes introduced in metapac prevent me from creating a PR against the main branch right now.