Add USB driver

[HaoboGu]

No description provided.

[andelf]

To handle DM/DP reuse in HPM5300(QFN48 and LQFP64):

Add a hpm5300-usb-pin-reuse feature, then if one wants to enable USB, it can be selected by

features = ["hpm5301", "hpm5300-usb-pin-reuse"]

This feature is disabled by default, which is safe.

impl<'d> Usb<'d> {
   pub fn new(peri: impl Peripheral<P = T> + 'd, 
             #[cfg(feature="hpm5300-usb-pin-reuse")] dp: impl Peripheral<P = impl DpPin<T>> + 'd, 
             #[cfg(feature="hpm5300-usb-pin-reuse")] dm: impl Peripheral<P = impl DmPin<T>> + 'd) 
     -> Self { ... }
}