USB: serial: whiteheat: fix line-speed endianness

Add missing endianness conversion when setting the line speed so that
this driver might work also on big-endian machines.

Also use an unsigned format specifier in the corresponding debug
message.

Signed-off-by: Johan Hovold <johan@kernel.org>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20191029102354.2733-3-johan@kernel.org


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