jtag/drivers/xds110: Fix compiler warning.

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

Simplify the code a little. The number of bytes written is already
checked in usb_write().

Signed-off-by: Tim Newsome <tim@sifive.com>
Change-Id: Ibada85dcccfca6f1269c584cdbc4f2e3b93bb8f3
Reviewed-on: https://review.openocd.org/c/openocd/+/7813
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Jan Matyas <jan.matyas@codasip.com>

src/jtag/drivers/xds110.c

@@ -579,9 +579,6 @@ static bool usb_get_response(uint32_t *total_bytes_read, uint32_t timeout)
 
 static bool usb_send_command(uint16_t size)
 {
-	int written;
-	bool success = true;
-
 	/* Check the packet length */
 	if (size > USB_PAYLOAD_SIZE)
 		return false;
@@ -596,13 +593,7 @@ static bool usb_send_command(uint16_t size)
 	size += 3;
 
 	/* 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;
+	return usb_write(xds110.write_packet, (int)size, NULL);
 }
 
 /***************************************************************************