Documentation: USB: fix example bulk-message timeout

USB bulk-message timeouts are specified in milliseconds and should
specifically not vary with CONFIG_HZ.

Use a fixed five-second timeout in the "Writing USB Device Drivers"
example.

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20211025115159.4954-2-johan@kernel.org


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