IB/ehca: Prevent sending UD packets to QP0

The IB spec doesn't allow packets to QP0 sent on any other VL than VL15.
Hardware doesn't filter those packets on the send side, so we need to do
this in the driver and firmware.

As eHCA doesn't support QP0, we can just filter out all traffic going to
QP0, regardless of SL or VL.

Signed-off-by: Joachim Fenkes <fenkes@de.ibm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>