Add initial ADC/GPIO implementation for ESP32-H2

[jessebraham]

@SergioGasquez was able to test and verify the example on hardware for me. Still need the AF signals and what not, but gives us a base to build off of at least.

(A passing CI run can be found here)

[bjoernQ]

Code looks good to me! Cannot verify it on hardware currently

[bjoernQ]

#[cfg_attr(not(any(esp32, riscv)), path = "adc/xtensa.rs")] made me think twice about what's happening here ... while it's certainly correct the previous version was easier to understand (given there won't be more Xtensas in future)

This adds ADC but not the adc-example? Not a problem - just curious

[JurajSadel]

I'll verify on real HW tomorrow (I don't have H2 with me at the moment :D )

[jessebraham]

@bjoernQ fair enough, that's been reverted. Not sure why I changed it in the first place TBH 🤷🏻‍♂️

ADC stuff is just sort of intermingled with the GPIO stuff, so I included those bits. Didn't test or anything, guess I could remove it but I think it's fine to include for now.

[JurajSadel]

LGTM, both examples (hello_world and blinky) work on real H2 chip correctly.
We have some warnings

warning: unused variable: `system`
   --> /home/ubuntu/esp-hal/esp-hal-common/src/system.rs:502:13
    |
502 |         let system = unsafe { &*SystemPeripheral::PTR };
    |             ^^^^^^ help: if this is intentional, prefix it with an underscore: `_system`
    |
    = note: `#[warn(unused_variables)]` on by default

warning: unused variable: `peripheral`
   --> /home/ubuntu/esp-hal/esp-hal-common/src/system.rs:501:30
    |
501 |     pub fn enable(&mut self, peripheral: Peripheral) {
    |                              ^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_peripheral`

warning: `esp-hal-common` (lib) generated 2 warnings (run `cargo fix --lib -p esp-hal-common` to apply 2 suggestions)
warning: unused variable: `clocks`
  --> examples/hello_world.rs:17:9
   |
17 |     let clocks = ClockControl::configure(system.clock_control, CpuClock::Clock96MHz).freeze();
   |         ^^^^^^ help: if this is intentional, prefix it with an underscore: `_clocks`

but I guess we will clear them along the way.

[MabezDev]

LGTM! Can't test, but the code looks fine to me.