[TF-A] Deprecation notification of Socionext Uniphier, Arm fvp_ve, Broadcom Stingray platforms

Hello,

During a recent code ownership cleanup we have identified three platforms that lack designated code owners: Socionext Uniphier, Arm fvp_ve, Broadcom Stingray platforms. All three have not had any significant activity for some time now and as such we are going to mark them as deprecated. The patches to do that are here: https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/53842. We will go ahead with them in the next week or so unless we hear any objections.

These platforms will not be removed until after the next v2.16 release scheduled for later this year. We will not proceed with removal if code owners are found before then.

Thanks, Boyan