[TF-A] Pointer Authentication keys

Hi,

From the initial read of the Arm ARM, there are multiple keys (instruction, data) provided for authenticating pointers. But the current implementation only writes IA key [1].

I would like to understand the thought process behind programming only one key here. AFAIU, we should enable all keys - IA, IB, DA, DB.

-Varun

[1] https://review.trustedfirmware.org/plugins/gitiles/TF-A/trusted-firmware-a/+...