scp_v2.14: Release notes for SCP-firmware v2.14

Update the change log to summarise the changes included in this release.

Signed-off-by: khaled ali ahmed <khaled.aliahmed@arm.com>
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
Change-Id: I919afa199179d78defd28841a1df11f52b1fff6d