staging: line6: wrap comment to 80 chars in driver.c

Fix the following checkpatch.pl warning:

  WARNING: line over 80 characters
  #1107: FILE: staging/line6/driver.c:523:
  +       /* Wait for data length. We'll get a couple of 0xff until length arrives. */

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>