Netlink is used to communicate with the greybus kernel.
Add a preliminary support of netlink.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>

This application connects to greybus netlink host device.
The main is goal is to give a way to resgister
a host device driver in user space.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>