ANDROID: dma-buf: Make DMA-BUF sysfs stats kobjects not send uevents

DMA-BUF per-buffer attachment stats are present at
/sys/kernel/dma-buf/buffers/<ino>/attachments. Since a kset of name
'attachment' is created everytime a buffer is allocated, disable
uevents from the kset to avoid their userspace overhead.

The ksets 'dma-buf' and 'buffers' do not need uevents disabled since
they are emitted just once but the patch does it for uniformity.

Bug: 186155231
Change-Id: I29009dd2aa0bc018c18bca7a1e0a068f4480cf13
Signed-off-by: Hridya Valsaraju <hridya@google.com>