USB: serial: keyspan_usa: add proper SPDX lines for .h files

The keyspan_usa??msg.h files are under a BSD-3 style license, so
properly label them as such with a SPDX line at the top of the file.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

USB Serial Keyspan: add support for USA-49WG & USA-28XG

Add support for Keyspan adapters: USA-49WG and USA-28XG

Signed-off-by: Lucy P. McCoy <lucy@keyspan.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>