qemu: add a build and boot test with encrypted BL31 using PSA Crypto

Add a build and boot test for QEMU with encrypted BL31, utilizing PSA
Crypto API support.

Change-Id: I5a4301fcff49ce66b02ac87e345c6c84c8165aa2
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
3 files changed