Extract out code from virNodeDeviceGetParentHost into helpers - it's
going to be reused in upcoming patches to search on more fields

Create virNodeDeviceFindVPORTCapDef in order to return a virNodeDevCapsDefPtr
of the VPORT_OPS and virNodeDeviceFindFCParentHost to use the function and
generate an error message if the device doesn't have the capability.

Also clean up the processing in virNodeDeviceGetParentHost to remove
need for goto's.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>