IB/ipath: Verify host bus bandwidth to chip will not limit performance

There have been a number of issues where host bandwidth via HT or PCIe
to the InfiniPath chip has been limited in some fashion (BIOS,
configuration, etc.), resulting in user confusion.  This check gives a
clear warning that something is wrong and needs to be resolved.

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