docs(release): add change log for v2.5 release
docs(release): add change log for v2.5 release

Change log for trusted-firmware-a v2.5 release

Change-Id: I6ffc8a40d2cc3a18145b87f895acdc1400db485a
Signed-off-by: Madhukar Pappireddy <c854e377c0ff08e0fa4357b6357bedff114c98a6@arm.com>

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware