defconfig: Enable SELinux and its dependencies

To have more control over the access rights for different
user space needs, SELinux imposes mandatory access controls
on Linux. Which allows an administrator of a system to
define how applications and users can access different
resources such as files, devices, networks and inter-process
communication.

Change-Id: I1f33a97d5bfe2bae816f7ece98bec9ffed580d19
Signed-off-by: Biswajit Paul <biswajitpaul@codeaurora.org>