jf-common: only build selinux in kernel if we want it

Change-Id: I11800c2432cc98e89858d971126b4a5db1d1ac7b
Merge "jf-common: only build selinux in kernel if we want it" into cm-10.1
Merge pull request #25 from CyanogenMod/cm-10.1

Pull request CM-10.1