Revert "gpu: ion: Add ioctls for prefetching/draining pools"

This reverts commit c2821d99d755e24db83af755da0628e41fd7a76e.
Revert "gpu: ion: Add support for heap walking"

This reverts commit 6f56136a7642efa62adec5f16cdf496fc5d6f409.
Revert "ion: fix copy paste derp"

This reverts commit 8506b602ef88a622788c97fb8c22f3cd6b64aa8e.
Revert "gpu: ion: Add pooling of CMA allocations"

This reverts commit 5c2847669438c242eb94fc0e93089f2b4288d6c3.
Revert "gpu: ion: Add pooling of CMA allocations"

This reverts commit 014063fac9f695ee4af1e26ecefbcc79054abcd6.