IB/{rdmavt, hfi1, qib}: Self determine driver name

Currently the HFI and QIB drivers allow the IB core to assign a unit
number to the driver name string.

If multiple devices exist in a system, there is a possibility that the
device unit number and the IB core number will be mismatched.

Fix by using the driver defined unit number to generate the device
name.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>