samsung/qcom-common: Move CAF variant flags to device repos

Not everything inheriting this repo will be using the same CAF repos (eg. MSM8974 uses
caf-bfam).

Change-Id: I7d3ce0b75b4f12534853abf99b41b579b48405fa
Merge pull request #2 from omnirom/android-4.4

samsung/qcom-common: Move CAF variant flags to device repos