[TF-M] Mailbox mechanism changed into partition

Hi,

Thank Chris made a couple of changes to move the mailbox mechanism from a kernel-coupled one into a partition-based one, which simplifies the programming model much.

And mailbox-related platforms (musca-b1 secure enclave and corstone 1000) may get affected after merged, please mentioned platform owners take a try on these patches. Another solution is we can merge them and then fix the problems found.

Will wait for one more week for the last patch (Patches no affecting platforms out of PSoC are merged already).

I think checkout this one should bring all related changes into local: https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/12311

Feel free to comment, thanks.

/Ken