Docs: usb: update err() to pr_err() and replace __FILE__

update err() to pr_err() and replace __FILE__

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/2c477cb0cf5214ae9abf9a4a9de28fcb38f90070.1635591623.git.philipp.g.hortmann@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>