I've set my power stage to `LDO` - this works fine now, however I've got `config.rcc.sys = Sysclk::PLL1_P; // 400 Mhz` https://github.com/embassy-rs/embassy/blob/main/examples/stm32h7/src/bin/adc.rs#L40 with vos0 enabled (see https://github.com/embassy-rs/embassy/blob/main/examples/stm32h7/src/bin/adc.rs#L40 but set as `VoltageScale::Scale0`).

However, the board still boots at 400MHz. see `sys: Some(Hertz(400000000))` below

```
0.000000 DEBUG rcc: Clocks { csi: Some(Hertz(4000000)), hclk1: Some(Hertz(200000000)), hclk2: Some(Hertz(200000000)), hclk3: Some(Hertz(200000000)), hclk4: Some(Hertz(200000000)), hse: None, hsi: Some(Hertz(64000000)), hsi48: Some(Hertz(48000000)), i2s_ckin: None, lse: None, lsi: None, pclk1: Some(Hertz(100000000)), pclk1_tim: Some(Hertz(200000000)), pclk2: Some(Hertz(100000000)), pclk2_tim: Some(Hertz(200000000)), pclk3: Some(Hertz(100000000)), pclk4: Some(Hertz(100000000)), per: None, pll1_q: Some(Hertz(100000000)), pll2_p: None, pll2_q: None, pll2_r: None, pll3_p: None, pll3_q: None, pll3_r: None, rtc: Some(Hertz(32000)), sys: Some(Hertz(400000000)) }
└─ embassy_stm32::rcc::set_freqs @ /Users/mdesilva/.cargo/git/checkouts/embassy-9312dcb0ed774b29/4c7ed5e/embassy-stm32/src/fmt.rs:130 
0.000000 INFO  Booting up...
└─ stm32h747_async_quickstart::____embassy_main_task::{async_fn#0} @ src/main.rs:44  
```

My working demo is here https://github.com/bsodmike/arduino-giga-r1-wifi-stm32h747xi-async-quickstart/blob/master/src/main.rs#L39