Revert "ion: Snapshot for 4.12 kernel upgrade"

This reverts commit b57ff724 ("ion: Snapshot for 4.12 kernel
upgrade").
Revert ION 4.9 kernel snapshot changes so that we can move to upstream
ION.
However keep changes to the following files:
include/linux/msm_dma_iommu_mapping.h
include/trace/events/kmem.h

Change-Id: Ia81ea76d16a6cba217a3434b9a854c0e5705ab24
Signed-off-by: Liam Mark <lmark@codeaurora.org>