topology: Fix incorrect license in source comments.

The topology source files had the wrong licence specified in the
comments when initially upstreamed. The topology source files are all
licensed under the LGPL-2.1 and not the GPLv2.

All earlier versions of the alsa-lib topology source files must be
considered LGPL-2.1 like the other source files in alsa-lib and also
as specified in the alsa-lib COPYING file.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>