commit c07d0073 upstream.

Add a write memory barrier to make sure that descriptors are actually
written to memory, before ringing the doorbell.
Signed-off-by: NFaiz Abbas <faiz_abbas@ti.com>
Acked-by: NAdrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>