drm/i915: Clear the pending_gpu_fenced_access flag at the start of execbuffer

Otherwise once we use the buffer with a BLT command on gen2/3, we will
always regard future command submissions as continuing the fenced
access. However, now that we flush/invalidate between every batch we can
drop this pessimism.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -413,6 +413,7 @@ i915_gem_execbuffer_reserve(struct intel_ring_buffer *ring,
 
 		obj->base.pending_read_domains = 0;
 		obj->base.pending_write_domain = 0;
+		obj->pending_fenced_gpu_access = false;
 	}
 	list_splice(&ordered_objects, objects);