16550 UART driver FLAGRANTLY DISREGARDS doc comment on Read trait

when used for non-blocking reads anyway. we've got this: ``` impl io::Read for Lock<'_, Nonblocking> { fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { for byte in buf.iter_mut() { *byte = self.inner.read_nonblocking()?; } Ok(buf.len()) } } ``` but on `trait mycelium_util::io::Read: ``` /// # Errors /// /// If this function encounters any form of I/O or other error, an error /// variant will be returned. If an error is returned then it must be /// guaranteed that no bytes were read. ``` so if we're reading a buffer of size >1 and there's an error (say, no more data to read so you WouldBlock), we drop the read bytes on the floor. here i think we'd be ok by returning however many bytes _were_ read until the WouldBlock, if that was the error, but i think in general we probably want a more verbose read() variant that always returns like, `(usize, Result<(), Error>)` or something. (i did exactly the same thing as `myceium_util::io::Read`'s requirement in yaxpeax's reader type because posix brain lol)