The firmware only asks for one dummy packet at a time, but sometimes we
are unable to provide it before a FW timer expires. When this happens,
the FW will re-request the dummy packet. If a packet is still queued in
the driver queues, do nothing in this case.

This prevents spurious dummy packets from clogging up the VO AC.
Signed-off-by: NArik Nemtsov <arik@wizery.com>
Signed-off-by: NEliad Peller <eliad@wizery.com>
Signed-off-by: NLuciano Coelho <coelho@ti.com>