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: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Piotr Haber <phaber@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>