[TF-M] SVC handlers refining

Hello,

For isolation levels > 1, partitions need to SVC for PSA APIs. To improve the efficiency of this call type, the SVC handler needs to be simplified.

Currently, there are several obvious places to be improved:

- Handlers in C have multiple-level function calling; - There are a couple of checks in the handler routine that can be refined.

And, to take advantage of instruction TBB, the switch/case number needs to be linear - but it is not always stable hence needs to investigate if a handmade function table would be more stable.

The leading patches are here: https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/20644

Feel free to comment or reply in this thread.

Thanks.

/Ken