commit 1d816b6e upstream.

When receiving a NDLC PCB_SYNC_ACK the pending data was never
removed from ack_pending_q and cleared.
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>