dmabuf_dump: Make output more readable and debug friendly

- Get rid of the PSS number that didn't make sense.
- Fix double counting in per-process size when buffers had file
  descriptors and mmap'ed
- Make the output much more readable
- Print totals where they make sense.
- Dont print per-process fd and map refs separately, total ref count per
  process is sufficient.

Bug: 135668399
Test: dmabuf_dump (on AOSP blueline)

Change-Id: I10dc0a332d49110dd68f0eaa94a326679361deea
Merged-In: I10dc0a332d49110dd68f0eaa94a326679361deea
Signed-off-by: Sandeep Patil <sspatil@google.com>