Otherwise the error status can be PSA_ERROR_INVALID_SIGNATURE instead of the
expected PSA_ERROR_NOT_SUPPORTED in some configurations. For example, the
RSA verification code currently checks the signature size first whenever
PSA_KEY_TYPE_RSA_PUBLIC_KEY is enabled, and only gets into
algorithm-specific code if this passes, so it returns INVALID_SIGNATURE even
if the specific algorithm is not supported.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>