hey all, can anyone help me figure out why the usb_serial.rs example (https://github.com/embassy-rs/embassy/blob/main/examples/stm32l4/src/bin/usb_serial.rs) is not working? when connecting the usb i get the following in my dmesg
```
usb 1-2.4.2: new low-speed USB device number 67 using xhci_hcd
usb 1-2.4.2: device descriptor read/64, error -32
usb 1-2.4.2: device descriptor read/64, error -32
usb 1-2.4.2: new low-speed USB device number 68 using xhci_hcd
usb 1-2.4.2: device descriptor read/64, error -32
usb 1-2.4.2: device descriptor read/64, error -32
usb 1-2.4-port2: attempt power cycle
usb 1-2.4.2: new low-speed USB device number 69 using xhci_hcd
usb 1-2.4.2: Device not responding to setup address.
usb 1-2.4.2: Device not responding to setup address.
usb 1-2.4.2: device not accepting address 69, error -71
usb 1-2.4.2: new low-speed USB device number 70 using xhci_hcd
usb 1-2.4.2: Device not responding to setup address.
usb 1-2.4.2: Device not responding to setup address.
usb 1-2.4.2: device not accepting address 70, error -71
usb 1-2.4-port2: unable to enumerate USB device
```

i had to edit the clocks configuration (which is probably the cause of the issue) because "Hsi48Config" is not available on my stm32l746rg

here's my clocks configuration:
```
let mut config = Config::default();
    // set the internal clock to run at max (80MHz)
    config.rcc.hsi = true;
    config.rcc.hse = Some(embassy_stm32::rcc::Hse {
        freq: Hertz(8_000_000),
        mode: embassy_stm32::rcc::HseMode::Oscillator,
    });
    config.rcc.pll = Some(embassy_stm32::rcc::Pll {
        source: embassy_stm32::rcc::PllSource::HSE,
        mul: embassy_stm32::rcc::PllMul::MUL10,
        divp: Some(embassy_stm32::rcc::PllPDiv::DIV7),
        divq: Some(embassy_stm32::rcc::PllQDiv::DIV2),
        divr: Some(embassy_stm32::rcc::PllRDiv::DIV2),
        prediv: embassy_stm32::rcc::PllPreDiv::DIV1,
    });
    // USB
    config.rcc.pllsai1 = Some(embassy_stm32::rcc::Pll {
        source: embassy_stm32::rcc::PllSource::HSE,
        prediv: embassy_stm32::rcc::PllPreDiv::DIV1,
        mul: embassy_stm32::rcc::PllMul::MUL12,
        divp: None,
        divq: Some(embassy_stm32::rcc::PllQDiv::DIV2),
        divr: None,
    });
    config.rcc.mux.clk48sel = embassy_stm32::rcc::mux::Clk48sel::PLLSAI1_Q;
    config.rcc.sys = embassy_stm32::rcc::Sysclk::PLL1_R;
    config.rcc.ahb_pre = embassy_stm32::rcc::AHBPrescaler::DIV2;
    config.rcc.apb1_pre = embassy_stm32::rcc::APBPrescaler::DIV1;
    config.rcc.apb2_pre = embassy_stm32::rcc::APBPrescaler::DIV1;
    config.rcc.mux.adcsel = embassy_stm32::rcc::mux::Adcsel::SYS;
```

any idea?