Fix bugs in example programs: change argc == 0 to argc < 2

Signed-off-by: Aditya Deshpande <aditya.deshpande@arm.com>
diff --git a/programs/ssl/ssl_mail_client.c b/programs/ssl/ssl_mail_client.c
index 643d3c2..6f1dc1c 100644
--- a/programs/ssl/ssl_mail_client.c
+++ b/programs/ssl/ssl_mail_client.c
@@ -367,7 +367,7 @@
     mbedtls_pk_init(&pkey);
     mbedtls_ctr_drbg_init(&ctr_drbg);
 
-    if (argc == 0) {
+    if (argc < 2) {
 usage:
         mbedtls_printf(USAGE);