pci: return the found index when query suceeds
pci: return the found index when query suceeds

Signed-off-by: Reto Achermann <66f6ea3e040423755b3cf26edfe6c7fb1f9adc27@inf.ethz.ch>

BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,kishoredbn/barrelfish,kishoredbn/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,kishoredbn/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,kishoredbn/barrelfish,BarrelfishOS/barrelfish,kishoredbn/barrelfish,kishoredbn/barrelfish