Revert "staging: android: ion: Remove crufty cache support"

This reverts commit 5dc3bafb ("staging: android: ion: Remove crufty
cache support").
Revert removing of ION cache support since cache support is still required
for memory allocated from buddy.

Change-Id: I51a467099060d9626497c3f7800b708f82e9d283
Signed-off-by: Liam Mark <lmark@codeaurora.org>