That appears to be leaking from the head gasket.
Suzuki recommends tightening the header bolts every 4,000 miles (concurrent with valve clearance check); this may be the reason why. Get a torque wrench and try following the repair manual procedure for slacking and re-torquing the head bolts. Don't forget the front bolt you have in the photo and watch the torque values. I think that one is in inch-pounds and doesn't take much.
If re-torquing doesn't solve the leak you will unfortunately need to replace the head gasket which is fairly involved.
The bike doesn't appear to be leaking much oil in your photo. You could just embrace the dirty bike look and leave it alone.