sandbox: Prepare API change for files greater than 2GB

Change the internal sandbox functions to use loff_t for file offsets.

Signed-off-by: Suriyan Ramasami <suriyan.r@gmail.com>

Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/include/os.h b/include/os.h
index 0230a7f..e3645e0 100644
--- a/include/os.h
+++ b/include/os.h
@@ -217,9 +217,10 @@
  * Get the size of a file
  *
  * @param fname		Filename to check
- * @return size of file, or -1 if an error ocurred
+ * @param size		size of file is returned if no error
+ * @return 0 on success or -1 if an error ocurred
  */
-ssize_t os_get_filesize(const char *fname);
+int os_get_filesize(const char *fname, loff_t *size);
 
 /**
  * Write a character to the controlling OS terminal