dma-buf: pass flags into dma_buf_fd.

We need to pass the flags into dma_buf_fd at this point,
so the flags end up doing the right thing for O_CLOEXEC.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Rob Clark <rob@ti.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>