spec: Correct License field
spec: Correct License field

The project contains code that is "GPLv2 with exceptions or MIT", code
that is "LGPLv2+ or MIT" and code that is "MIT" licensed. Unify in a
single expression.

Signed-off-by: Guillem Jover <6f269179bd29909dac5e2359bafef574d0759c09@hadrons.org>

axboe/liburing,axboe/liburing,axboe/liburing