libinit: Allow device to override source files

* Using TARGET_LIBINIT_DEFINES_FILE := "path"

Change-Id: Idf39eb7b5ce825aab63fe2fd185d4e20e731b3b2
Signed-off-by: Brandon McAnsh <brandon.mcansh@gmail.com>
Merge branch 'kitkat' of github.com:AOKP/device_samsung_qcom-common into kitkat