selinux: Add boundary check in put_entry()

[ Upstream commit 15ec76fb29be31df2bccb30fc09875274cba2776 ]

Just like next_entry(), boundary check is necessary to prevent memory
out-of-bound access.

Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>