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: I8aaa0ddfcd4a340a94cbedb0f4431625fd057618
Signed-off-by: Kurva Harish <hkurva@codeaurora.org>
[imaund@codeaurora.org: Resolved context conflicts]
Signed-off-by: Ian Maund <imaund@codeaurora.org>