net/enic: extend flow handler to support VF representors

net/enic: extend flow handler to support VF representors

VF representor ports can create flows on VFs through the PF flowman
(Flow Manager) instance in the firmware. These flows match packets
egressing from VFs and apply flowman actions.

1. Make flow handler aware of VF representors
When a representor port invokes flow APIs, use the PF port's flowman
instance to perform flowman devcmd. If the port ID refers to a
representor, use VF handle instead of PF handle.

2. Serialize flow API calls
Multiple application thread may invoke flow APIs through PF and VF
representor ports simultaneously. This leads to races, as ports all
share the same PF flowman instance. Use a lock to serialize API
calls. Lock is used only when representors exist.

3. Add functions to create flows for implicit representor paths
There is an implicit path between VF and its representor. The
functions below create flow rules to implement that path.
- enic_fm_add_rep2vf_flow()
- enic_fm_add_vf2rep_flow()

The flows created for representor paths are marked as internal. These
are not visible to application, and the flush API does not destroy
them. They are automatically deleted when the representor port stops
(enic_fm_destroy).

Signed-off-by: Hyong Youb Kim <hyonkim@cisco.com>
Reviewed-by: John Daley <johndale@cisco.com>