[tftp] Reduce windowSize

Change-Id: Id445cf1d7dd39acd018f5a70f59db30e0a362dd9
diff --git a/tftp/tftp.go b/tftp/tftp.go
index 980c5d8..7fcf055 100644
--- a/tftp/tftp.go
+++ b/tftp/tftp.go
@@ -25,7 +25,10 @@
 	retries      = 5               // default number of retries
 	blockSize    = 1024            // default block size
 	datagramSize = 1028            // default datagram size
-	windowSize   = 256             // default window size
+	// Throttle bootserver transfers to avoid issues with the Monoprice adapters
+	// overflowing buffers when combined with the board performance
+	// TODO: Consume a -w value from the build or just use bootserver.
+	windowSize = 10 // default window size
 )
 
 const (