nfp: flower: read extra feature support from fw

Extract the _abi_flower_extra_features symbol from the fw which gives a 64
bit bitmap of new features (on top of the flower base support) that the fw
can offload. Store this bitmap in the priv data associated with each app.
If the symbol does not exist, set the bitmap to 0.

Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>