gpu: Add ColdPlug of VFIO devices with devManager

If we have a VFIO device and cold-plug is enabled
we mark each device as ColdPlug=true and let the VFIO
module do the attaching.

Signed-off-by: Zvonko Kaiser <zkaiser@nvidia.com>

src/runtime/pkg/device/manager/utils_test.go

@@ -31,7 +31,7 @@ func TestIsVFIO(t *testing.T) {
 	}
 
 	for _, d := range data {
-		isVFIO := isVFIO(d.path)
+		isVFIO := IsVFIO(d.path)
 		assert.Equal(t, d.expected, isVFIO)
 	}
 }