netdev-genl: spec: Add PID in netdev netlink YAML spec

Add support in netlink spec(netdev.yaml) for PID of the
NAPI thread. 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/170147335301.5260.11872351477120434501.stgit@anambiarhost.jf.intel.com


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