RDMA/cxgb3: Don't crash kernel just because IDR is full

cxgb3 driver properly handles errors returned by IDR, so there is no
need to have special case (kernel crash) just because IDR is full.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>