Merge remote-tracking branch 'origin/release/1.8.x' into 'origin/master'

Accomodate release note changes after TF-M v1.8.1 release

Signed-off-by: Antonio de Angelis <antonio.deangelis@arm.com>
Change-Id: Ibbf0bc348c88fcd343614ee660c506237ff633b9