remove NULL guard

Signed-off-by: Ben Taylor <ben.taylor@linaro.org>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 7fbb0b5..4635a85 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -4462,7 +4462,7 @@
 #endif /* MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED */
 
 #if defined(MBEDTLS_SSL_ASYNC_PRIVATE)
-    if (ssl->conf != NULL && ssl->conf->f_async_cancel != NULL && handshake->async_in_progress != 0) {
+    if(ssl->conf->f_async_cancel != NULL && handshake->async_in_progress != 0) {
         ssl->conf->f_async_cancel(ssl);
         handshake->async_in_progress = 0;
     }