Revert "USB: serial: ch341: fix character loss at high transfer rates"

This reverts commit 3c18e9b.

These devices do not appear to send a zero-length packet when the
transfer size is a multiple of the bulk-endpoint max-packet size. This
means that incoming data may not be processed by the driver until a
short packet is received or the receive buffer is full.

Revert back to using endpoint-sized receive buffers to avoid stalled
reads.

Reported-by: Paul Größel <pb.g@gmx.de>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=214131
Fixes: 3c18e9b ("USB: serial: ch341: fix character loss at high transfer rates")
Cc: stable@vger.kernel.org
Cc: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20210824121926.19311-1-johan@kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/ch341.c

@@ -851,7 +851,6 @@ static struct usb_serial_driver ch341_device = {
 		.owner	= THIS_MODULE,
 		.name	= "ch341-uart",
 	},
-	.bulk_in_size      = 512,
 	.id_table          = id_table,
 	.num_ports         = 1,
 	.open              = ch341_open,