Move from memset to memset_s.

This adds the extra bounds checks and panics if there is a violation.

Change-Id: I9db3ca44be4f9c39964d912b57fe7b68e2792bc1
diff --git a/src/fdt.c b/src/fdt.c
index b781a72..f02864a 100644
--- a/src/fdt.c
+++ b/src/fdt.c
@@ -136,7 +136,7 @@
 	uint32_t begin = be32toh(hdr->off_dt_struct);
 	uint32_t size = be32toh(hdr->size_dt_struct);
 
-	memset(node, 0, sizeof(*node));
+	memset_s(node, sizeof(*node), 0, sizeof(*node));
 
 	/* Check the magic number before anything else. */
 	if (hdr->magic != be32toh(FDT_MAGIC)) {