conn: windows: set count=0 on retry

When retrying, if count is not 0, we forget to dequeue another request,
and so the ring fills up and errors out.

Reported-by: Sascha Dierberg <dierberg@dresearch-fe.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

conn/bind_windows.go

@@ -357,6 +357,7 @@ func (bind *afWinRingBind) Receive(buf []byte, isOpen *uint32) (int, Endpoint, e
 	var count uint32
 	var results [1]winrio.Result
 retry:
+	count = 0
 	for tries := 0; count == 0 && tries < receiveSpins; tries++ {
 		if tries > 0 {
 			if atomic.LoadUint32(isOpen) != 1 {