USB: oti6858: cleanup

- Rename the copied buffer functions from pl2303 to oti6858 to avodi
  confusion
- Initialise speeds properly
- Use modern baud rate handling
- Remove GSERIAL/SSERIAL ioctl hacks that reference termios unlocked

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>