jtag/drivers/xds110: Fix compiler warning.

Compiler would complain that `written` was used without being
initialized.

Signed-off-by: Tim Newsome <tim@sifive.com>
Change-Id: Ibada85dcccfca6f1269c584cdbc4f2e3b93bb8f3

src/jtag/drivers/xds110.c

@@ -598,10 +598,6 @@ static bool usb_send_command(uint16_t size)
 	/* Send the data via the USB connection */
 	success = usb_write(xds110.write_packet, (int)size, &written);
 
-	/* Check if the correct number of bytes was written */
-	if (written != (int)size)
-		success = false;
-
 	return success;
 }