IB/ipath: Changes to support PIO bandwidth check on IBA7220

The IBA7220 uses a count-based triggering mechanism, and therefore
can't use the same bandwidth verification mechanism as older chips.

To support the 7220, allow enabling and disabling armlaunch errors on
application request.  Minor robustness improvements as well.

Signed-off-by: Dave Olson <dave.olson@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>