netlink: add netlink handler for gpause (-a)

Implement "ethtool -a <dev>" subcommand using ETHTOOL_MSG_PAUSE_GET netlink
message. This retrieves and diaplays device pause parameters, traditionally
provided by ETHTOOL_GPAUSEPARAM ioctl request.

Also register the callback with monitor code so that the monitor can
display ETHTOOL_MSG_PAUSE_NTF notifications. When in monitor mode,
negotiated status is not displayed.

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
6 files changed