Fix define and function names to conform to Mbed TLS rules

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 5ed06d3..1234543 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -4349,8 +4349,8 @@
 
            MBEDTLS_SSL_DEBUG_MSG( 3, ( "execute delayed server certificate verification" ) );
 
-           ret = ssl_parse_delayed_certificate_verify( ssl, authmode,
-                                                       chain, rs_ctx );
+           ret = mbedtls_ssl_parse_delayed_certificate_verify( ssl, authmode,
+                                                               chain, rs_ctx );
            if( ret != 0 )
                break;
 #endif /* MBEDTLS_DELAYED_SERVER_CERT_VERIFICATION */