ipoib: increase the non-cm queue length

When a packet needs fragmentation, it might generate more than 3 fragments.
With the queue length 3, all fragments are generated faster than the
queue is drained, which effectively drops fourth and later fragments on
the floor.

Submitted by: kib@
Approved by: hselasky (mentor)
MFC after: 1 week
Sponsored by: Mellanox Technologies