cifs: update internal module version number

To 2.28

Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsfs.h

@@ -156,5 +156,5 @@ extern int cifs_truncate_page(struct address_space *mapping, loff_t from);
 extern const struct export_operations cifs_export_ops;
 #endif /* CONFIG_CIFS_NFSD_EXPORT */
 
-#define CIFS_VERSION   "2.27"
+#define CIFS_VERSION   "2.28"
 #endif				/* _CIFSFS_H */