flite: fix license issue.

copy license from http://www.speech.cs.cmu.edu/flite/

 and include text

WARNING: flite-alsa: No generic license file exists for: flite in any provider

Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>