Tracing vm eviction is really the event we care about. For the cases we
evict everything, we still will get the trace.

v2: Add the drm device to the trace since we might not be the only
device in the system. (Chris)
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>