Update fence event path for kernel 4.10+

The sysfs path for controlling dma fence events changed yet again in
Linux 4.10, see kernel commit f54d1867005c3.

Test: adb shell atrace --list_categories | grep sync
Test: external/chromium-trace/systrace.py sync, check for dma_fence
      events in trace.html's event list
Change-Id: I45905cf199d5de3d5679151f19f8aa693adea5e1