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: Ia43f7cf84afe090186a16a2d3e4b30d011de8d4a
Signed-off-by: Ravi Kumar <rsiddoji@codeaurora.org>