brcmsmac: add copyright information for Canonical

Patches from Canonical involved the introduction of new source
files debug.[ch]. That coincided with other patches from Broadcom
introducing the same files.

Cc: Seth Forshee <seth.forshee@canonical.com>
Reviewed-by: NPieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: NPiotr Haber <phaber@broadcom.com>
Signed-off-by: NArend van Spriel <arend@broadcom.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmsmac/debug.h

 /*
  * Copyright (c) 2012 Broadcom Corporation
+ * Copyright (c) 2012 Canonical Ltd.
  *
  * Permission to use, copy, modify, and/or distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above