usblb: changed confusing instances of calling a usblb_{gadget|host} "dev"

Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
usblb: implemented the pullup gadget operation which spawns the host event.
now both ends of the bus spawn events (which do nothing)

Signed-off-by: Tal Shorer <tal.shorer@gmail.com>