ixgbe: fix vf lookup

ixgbe: fix vf lookup

Recent addition of code to find already allocated VFs failed to take
account that systems with 2 or more multi-port SR-IOV capable controllers
might have already enabled VFs.  Make sure that the VFs the function is
finding are actually subordinate to the particular instance of the adapter
that is looking for them and not subordinate to some device that has
previously enabled SR-IOV.

This bug exists in 3.2 stable as well as 3.3 release candidates.

CC: stable@vger.kernel.org
Reported-by: David Ahern <daahern@cisco.com>
(cherry picked from commit a4b08329c74985e5cc3a44b6d2b2c59444ed8079)
Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Tested-by: Robert E Garrett <robertX.e.garrett@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Joe Jin <joe.jin@oracle.com>