Switch to the real MIT license

Due to a copy/paste error, the COPYING file and subsequently created files
with the same content referred to the "Historical Permission Notice and
Disclaimer - sell variant", not the proper MIT license.

Replace with the proper MIT (Expat) license and add the use SPDX license
identifiers.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
2 jobs for wip/mit-license in 51 seconds (queued for 1 second)
Status Name Job ID Coverage
  Containers
passed fedora@container_build #8138704

00:00:10

 
  Build
passed fedora:32@default-build #8138705

00:00:40