Update the crate to use newer tock-registers and assembly syntax

[eupn]

First of all, thank you for this great crate!

I updated it to compile on recent stable rustc and to support the latest tock-registers crate and inline assembly syntax.

[eupn]

cc @jeandudey

[jeandudey]

Looks good to me 👍

Thanks for making this crate @mcdoll, really helpful :D. Any chance PRs can get reviewed (no rush, just so you also benefit from the changes)? We'll probably keep contributing some stuff we find along the way as we use the crate.

[mcdoll]

Hey, I am sorry, but I don't have access to the hardware at the moment and have generally abandoned the project (it was just for fun to try to adapt some tutorials that were floating around to an beaglebone - since that had way better documentation than the raspi). I think it might be better if you keep everything on your branch and if there is the possibility that we can switch the crate.io link to your branch, I am happy to do that.

[eupn]

Hi @mcdoll, sure, we'll then merge this branch into our fork's master branch. Feel free to update crate's Cargo.toml to set our fork as the repository value.

[sourcebox]

@mcdoll Do you think it's a risk to accept this PR? I mainly ask because you're the maintainer of this crate on crates.io. So it would be nice to have an released version there that can be used with stable.