docs: update code freeze & target date for v2.5
docs: update code freeze & target date for v2.5

Updated code freeze and release target date for v2.5 release.

Change-Id: I72850eed2aa77d3adecaf71d74e9ecebcc36d5b4
Signed-off-by: Madhukar Pappireddy <c854e377c0ff08e0fa4357b6357bedff114c98a6@arm.com>

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