dma-buf/fence: revert "don't wait when specified timeout is zero" (v2)

Reverts commit 847b19a3
	("dma-buf/fence: don't wait when specified timeout is zero")

When we don't call the wait function software signaling might never be
activated. This can cause infinite polling loops with unreliable interrupt
driven hardware.

v2: rebase on drm-next
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NChunming Zhou <david1.zhou@amd.com>
Reviewed-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>
  [sumits: reword commit msg for checkpatch warnings]
Link: http://patchwork.freedesktop.org/patch/msgid/1478553376-18575-2-git-send-email-alexander.deucher@amd.com

drivers/dma-buf/dma-fence.c

@@ -161,9 +161,6 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
 	if (WARN_ON(timeout < 0))
 		return -EINVAL;
 
-	if (timeout == 0)
-		return dma_fence_is_signaled(fence);
-
 	trace_dma_fence_wait_start(fence);
 	ret = fence->ops->wait(fence, intr, timeout);
 	trace_dma_fence_wait_end(fence);