dmabuf_dump: Remove per-device and attachment stats

Creating a separate sysfs directory for each dmabuf attachment
adds overhead that is quite significant in some fast paths.

Attachment stats are being removed from dmabuf sysfs stats

Remove the per-device and attachment stats from dmabuf_dump

Bug: 193226716
Bug: 193465681
Bug: 192621117
Test: dmabuf_dump -b
Change-Id: If3a67c07e8c013d76fe158f4a0260f1ec4153391
1 file changed