Update file names in comments

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/x509_oid.c b/library/x509_oid.c
index d05a36d..1637c1c 100644
--- a/library/x509_oid.c
+++ b/library/x509_oid.c
@@ -1,5 +1,5 @@
 /**
- * \file oid.c
+ * \file x509_oid.c
  *
  * \brief Object Identifier (OID) database
  *