IB/rdmavt: Add query gid support.

Addin query gid support. Rdmavt still relies on the driver to maintain
the gid table. Rdmavt simply calls into the driver to retrive the guid
for a particular port.

Reviewed-by: Harish Chegondi <harish.chegondi@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>