dma-buf/fence: don't wait when specified timeout is zero

When specified timeout is zero for fence_wait_timeout, just check if the fence
is signaled or not without wait.

Signed-off-by: Jammy Zhou <Jammy.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-By: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>