DSME: Track "charger" connection with the usbtracker module

Based on the connection state we decide if a charger is connected or not.
When a USB cable is connected we should be charging (except for error conditions).

Fixes: JB#6580

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

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
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>
Merge pull request #1 from philippedeswert/master

Merge Philippe's changes