selinux: Relocate ss_initialized to a separate 4k page

We need to relocate ss_initialized to a separate 4k page
to enable EL2 Hypervisor to monitor changes to this variable
using ARM stage 2 MMU. We will avoid getting page faults from
un-related data as the MMU granularity is configured to 4k.

Change-Id: I74a1e735d5f804a35ce5b7ffe8b8746e5f56201b
Signed-off-by: Zhen Kong <zkong@codeaurora.org>