USB: cp210x: increase the bulk-out buffer size to 256 byte

Increase the bulk-out buffer size from 64 to 256 byte.

This gives a significant increase in throughput already at 1Mbaud
(e.g. 710 instead of 640 KB/s) as well as lowered CPU usage.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/cp210x.c

@@ -138,6 +138,7 @@ static struct usb_serial_driver cp210x_device = {
 	.usb_driver		= &cp210x_driver,
 	.id_table		= id_table,
 	.num_ports		= 1,
+	.bulk_out_size		= 256,
 	.open			= cp210x_open,
 	.close			= cp210x_close,
 	.break_ctl		= cp210x_break_ctl,