Add ecdh_psa_shared_key flag to protect PSA privkey if imported

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 6329e0d..e13b3d9 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -632,6 +632,7 @@
     psa_key_type_t ecdh_psa_type;
     uint16_t ecdh_bits;
     mbedtls_svc_key_id_t ecdh_psa_privkey;
+    uint8_t ecdh_psa_shared_key;
     unsigned char ecdh_psa_peerkey[MBEDTLS_PSA_MAX_EC_PUBKEY_LENGTH];
     size_t ecdh_psa_peerkey_len;
 #endif /* MBEDTLS_USE_PSA_CRYPTO || MBEDTLS_SSL_PROTO_TLS1_3 */