(multiple): Use standard permission notice

(multiple): Use standard permission notice

A handful of source files were not using the MIT Expat text in
COPYING. Update these files to bring them inline with the rest,
standardizing on the MIT Expat text.

Signed-off-by: Yong Bakos <ybakos@humanoriented.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>