iw_cxgb4: remove BUG_ON() usage.

iw_cxgb4 has many BUG_ON()s that were left over from various enhancemnets
made over the years.  Almost all of them should just be removed.  Some,
however indicate a ULP usage error and can be handled w/o bringing down
the system.

If the condition cannot happen with correctly implemented cxgb4 sw/fw,
then remove the BUG_ON.

If the condition indicates a misbehaving ULP (like CQ overflows), add
proper recovery logic.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>