netdev-genl: spec: Extend netdev netlink spec in YAML for NAPI

Add support in netlink spec(netdev.yaml) for napi related information.
Add code generated from the spec.

Signed-off-by: Amritha Nambiar <amritha.nambiar@intel.com>
Reviewed-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
Link: https://lore.kernel.org/r/170147333119.5260.7050639053080529108.stgit@anambiarhost.jf.intel.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>