USB 2.0 HS

[mriise]

This is the beginnings of HS the protocol. Will close #39.

currently only makes interval generic to allow for Microseconds when the time comes.

also fixes a few clippy warnings.

[mriise]

For speed configuration I am currently thinking something along the lines of

pub enum UsbSpeed {
    Usb,
    Usb2(Usb2Speed),
}

pub enum Usb2Speed {
    FullSpeed,
    HighSpeed,
}

Usb 3.0 could be possible, but I am focusing on just getting high speed for this PR.