Initialise VF and PF representors in flower app.

Based in part on work by Benjamin LaHaise, Bert van Leeuwen and
Jakub Kicinski.
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>