bug fixing: let FPGA driver report correct traits when no SRIOV enabled
bug fixing: let FPGA driver report correct traits when no SRIOV enabled

Bug: when compute node did not enable SRIOV, only have PF on this
node, this driver cannot discover region and function ID traits in
driver_attribute objest.
This patch has fixed this bug.

Change-Id: I3984fc7a91467db7b8cc9b624fdf6a627dff7716

openstack/nomad