Yama: do not modify global sysctl table entry

When the sysctl table is constified, we won't be able to directly modify
it. Instead, use a table copy that carries any needed changes.

Suggested-by: PaX Team <pageexec@freemail.hu>
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --cc security/yama/yama_lsm.c
Simple merge