tls13: Do not use MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED
tls13: Do not use MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED

Use MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED
instead.

Signed-off-by: Ronald Cron <b35ff5b7ca26c4ae9b66b92f2cf34224c8e26b08@arm.com>

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