sysctl: Move sysctl_panic_on_stackoverflow to kernel/panic.c

sysctl: Move sysctl_panic_on_stackoverflow to kernel/panic.c

This is part of a greater effort to move ctl tables into their
respective subsystems which will reduce the merge conflicts in
kernel/sysctl.c.

Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Joel Granados <joel.granados@kernel.org>