bluez5: handle any quantum in a2dp-sink

Remove quantum limitation from a2dp-sink, and adjust how flushing is
done.

The "low-latency" A2DP codecs are not able to flush all data at once, so
for them flush based on a timeout, such that "excess samples" for each
quantum is bounded.  We also limit excess samples for the other A2DP
codecs, based on some testing on flaky headset/adapter combinations (for
most cases, this does not appear to matter).

Leave decision of packet sizes to the codecs. Currently, we send packets
based on min_latency, but sendinf full packets might help with stutter
on some headset/adapter combinations.  The slightly increased latency
hardly matters against the 100ms delays in BT headsets.

Bump codec API version.

spa/plugins/bluez5/sco-sink.c

@@ -66,6 +66,8 @@ struct props {
 };
 
 #define MAX_BUFFERS 32
+#define MIN_LATENCY	512
+#define MAX_LATENCY	1024
 
 struct buffer {
 	uint32_t id;