alsa: Fix sample rate negotiation (#441)

This change fixes the sample rate negotiation functionality, by making a comparison against the value of the slice and not the index.

device/alsa/alsa.go

@@ -281,7 +281,7 @@ func (d *ALSA) open() error {
 
 	var rate int
 	foundRate := false
-	for r := range rates {
+	for _, r := range rates {
 		if r < int(d.SampleRate) {
 			continue
 		}