Rename constant-time functions to have mbedtls_ct prefix

Rename functions to better suite with the module name.

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index def6c7b..0e802e9 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -1459,9 +1459,9 @@
         /* Check verify-data in constant-time. The length OTOH is no secret */
         if( len    != 1 + ssl->verify_data_len * 2 ||
             buf[0] !=     ssl->verify_data_len * 2 ||
-            mbedtls_cf_memcmp( buf + 1,
+            mbedtls_ct_memcmp( buf + 1,
                           ssl->own_verify_data, ssl->verify_data_len ) != 0 ||
-            mbedtls_cf_memcmp( buf + 1 + ssl->verify_data_len,
+            mbedtls_ct_memcmp( buf + 1 + ssl->verify_data_len,
                           ssl->peer_verify_data, ssl->verify_data_len ) != 0 )
         {
             MBEDTLS_SSL_DEBUG_MSG( 1, ( "non-matching renegotiation info" ) );