staging: android: ion: Track total memory allocations per heap

Add support to track the total amount of memory allocated by each ION
heap. This information makes it easier to identify if an ION client is
responsible for a memory leak.

Change-Id: I44638316b6462d28ec182f58b3b3e5cc99716f33
Signed-off-by: Liam Mark <lmark@codeaurora.org>