2 Function prevent this crate to be used on smaller hardware (ESP32)

[hcabel]

He, I wanted to use another crate that depend on this one (usbd-human-interface-device), on my ESP32-S3 and sadly it wouldn't compile :/

The reason is that ESP32 (and probably other microcontrollers) doesn't support AtomicU64 which is used by the bitvec crate that this one depends on.
Digging into this I realize that you only use bitvec in 2 function:

packed_struct.rs/packed_struct/src/types_num.rs

Line 667 in 0faff82

use bitvec::prelude::*;

and

packed_struct.rs/packed_struct/src/types_num.rs

Line 687 in 0faff82

use bitvec::prelude::*;

I've personally copied everything locally and commented those out (work fine now 👍) (not qualify enough to make a PR myself)

original Issue: dlkj/usbd-human-interface-device#164