security: fix a couple of sparse warnings

Fix a couple of sparse warnings for callers of
context_struct_to_string, which takes a *u32, not an *int.

These cases are harmless as the values are not used.

Signed-off-by: James Morris <jmorris@namei.org>
Acked-by: KaiGai Kohei <kaigai@ak.jp.nec.com>