Fix unused warning in ssl_tls.c

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index bf02318..d56bc5b 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -4131,8 +4131,8 @@
     ssl->alpn_chosen = NULL;
 #endif
 
-    int free_cli_id = 1;
 #if defined(MBEDTLS_SSL_DTLS_HELLO_VERIFY) && defined(MBEDTLS_SSL_SRV_C)
+    int free_cli_id = 1;
 #if defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE)
     if( partial != 0 )
         free_cli_id = 0;