usbtracker: * track dedicated charger, not only cable
            * only send signals when the connection status changes

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
Fix typo in variable name
Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
logic fixes

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
Add usb_moded query on start-up to know charger state

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>