conn: inch BatchSize toward being non-dynamic

There's not really a use at the moment for making this configurable, and
once bind_windows.go behaves like bind_std.go, we'll be able to use
constants everywhere. So begin that simplification now.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

conn/bind_windows.go

@@ -321,6 +321,8 @@ func (bind *WinRingBind) Close() error {
 	return nil
 }
 
+// TODO: When all Binds handle IdealBatchSize, remove this dynamic function and
+// rename the IdealBatchSize constant to BatchSize.
 func (bind *WinRingBind) BatchSize() int {
 	// TODO: implement batching in and out of the ring
 	return 1