net: flow: Add support for INGRESS_ROOT and EGRESS_ROOT

Ingress pipelines and egress pipelines can be different depending
on hardware archeticture. As such we need to provide a mechanism
to show both the ingress graph and egress graph.

This patch adds flags to the graph layout to indicate root node.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
net: flow: do nla_len checks
net: simplify ndo op naming scheme
net: flow: add new DYNAMIC flag

use the dynamic flag to indicate a table node can be used as a
container for create/delete table.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>