[TF-M] psa-arch-tests console baud rate

Triggered by Rays mail on slow RSA key pair generation, I built and tried to run the tests, but ran into a couple of issues:

1) I attempted to build it for the Musca A, but apparently that doesn't have enough RAM to run these tests

2) Switching to an MPS2+ with AN521 configuration I see that the baud rate on the UART appears wrong when running the tests.

mcuboot produces correct messages at 115200 bps, as does the normal ConfigRegression* tests, but the ConfigPsaApiTest* appears to produce just garbage.

Is there a setting I need to set to get any useful data on the terminal when running the ConfigPsaApiTests?

Cheers, Thomas