package/spandsp: bump version to 3.0.0

Reformatted hashes.

Switched upstream to freeswitch repo which is maintained by the author
of spandsp:
https://github.com/signalwire/freeswitch/issues/681#issuecomment-671498542

The previous project URL http://www.soft-switch.org/

 is not reachable
anymore.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>