programs_dh_client/server: Changed mdlen type to unsigned integer.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/programs/pkey/dh_client.c b/programs/pkey/dh_client.c
index 1b5ba40..e846914 100644
--- a/programs/pkey/dh_client.c
+++ b/programs/pkey/dh_client.c
@@ -59,7 +59,8 @@
 
     int ret = 1;
     int exit_code = MBEDTLS_EXIT_FAILURE;
-    size_t n, buflen, mdlen;
+    unsigned int mdlen;
+    size_t n, buflen;
     mbedtls_net_context server_fd;
 
     unsigned char *p, *end;
@@ -186,7 +187,7 @@
         goto exit;
     }
 
-    mdlen = mbedtls_md_get_size(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256));
+    mdlen = (unsigned int) mbedtls_md_get_size(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256));
     if (mdlen == 0) {
         mbedtls_printf(" failed\n  ! Invalid digest type\n\n");
         goto exit;