Return NOT_SUPPORTED according to the API contract
Return NOT_SUPPORTED according to the API contract

"retval = PSA_ERROR_NOT_SUPPORTED if alg is not supported"

Signed-off-by: Steven Cooreman <3aba90f1d379733e8874f60494a9cbe19be366cb@silabs.com>

ARMmbed/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls