net: flow_offload: fix flow_indr_dev_unregister path

If the representor is removed, then identify the indirect flow_blocks
that need to be removed by the release callback and the port representor
structure. To identify the port representor structure, a new
indr.cb_priv field needs to be introduced. The flow_block also needs to
be removed from the driver list from the cleanup path.

Fixes: 1fac52da

 ("net: flow_offload: consolidate indirect flow_block infrastructure")

Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>