Implement PRIVFLAGS_GET request to get private flags for a network device.
These are traditionally available via ETHTOOL_GPFLAGS ioctl request.
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>