Refactor the clock module, provide ROM functions via linker scripts

[jessebraham]

• Refactors clock.rs and clocks_ll into a common clock module
• Add a rom-functions linker script for each device's HAL
• Use the provided ROM functions instead of transmuting memory addresses
• Fix a warning about an unused import

[jessebraham]

This builds just fine locally for me, no idea why the S2 is failing on GHA.

[bjoernQ]

LGTM

[bjoernQ]

Code looks fine to me and I even tried to build the ESP32-S2 examples in WSL (to make sure there isn't a case-sensitivity issue with some file) - compiled fine for me

Still, I'm a bit concerned since it would be awful if all future CI builds would fail for S2

[bjoernQ]

One thing that is interesting: In the failing build it shows the invocation of the linker and it's missing "-nostartfiles" "-Wl,-Tlinkall.x" which should come from .cargo/config.toml

[bjoernQ]

Ok I know what is going on!

In https://github.com/esp-rs/esp-hal/blob/7f8a15ccf565a18eec466687de62829b20c6d5bd/.github/workflows/ci.yml#LL117C7-L117C16

The RUSTFLAGS get set which means it won't take the rustflags from .cargo/config.toml

Removing that from the build script should make CI happy again

[MabezDev]

LGTM! Much cleaner now :).

[jessebraham]

@bjoernQ good eye! Thank you so much that was driving me crazy 😁 That line should have been removed before the CI changes got merged so that was my bad anyway. Oh well, fixed now!