datapath: Allow for any level of nesting in flow attributes

datapath: Allow for any level of nesting in flow attributes

Upstream commit:
    openvswitch: Allow for any level of nesting in flow attributes

    nlattr_set() is currently hardcoded to two levels of nesting. This change
    introduces struct ovs_len_tbl to define minimal length requirements plus
    next level nesting tables to traverse the key attributes to arbitrary depth.

    Signed-off-by: Thomas Graf <tgraf@suug.ch>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Upstream: 81bfe3 ("openvswitch: Allow for any level of nesting in flow attributes")
Signed-off-by: Thomas Graf <tgraf@noironetworks.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>