IO: fix px4io uploader to work reliably on F7 platform.

- Missing get_sync() in verify function
- Allow some time to reboot before closing the serial port
  (closing the serial port drives TX low)

src/drivers/px4io/px4io_uploader.cpp

@@ -645,6 +645,13 @@ PX4IO_Uploader::verify_rev3(size_t fw_size_local)
 		return ret;
 	}
 
+	ret = get_sync();
+
+	if (ret != OK) {
+		log("did not receive CRC checksum");
+		return ret;
+	}
+
 	/* compare the CRC sum from the IO with the one calculated */
 	if (sum != crc) {
 		log("CRC wrong: received: %d, expected: %d", crc, sum);
@@ -657,11 +664,19 @@ PX4IO_Uploader::verify_rev3(size_t fw_size_local)
 int
 PX4IO_Uploader::reboot()
 {
+	int ret;
+
 	send(PROTO_REBOOT);
 	up_udelay(100 * 1000); // Ensure the farend is in wait for char.
 	send(PROTO_EOC);
 
-	return OK;
+	ret = get_sync();
+
+	if (ret == OK) {
+		up_udelay(10 * 1000);	// Ensure that we do not close UART too soon
+	}
+
+	return ret;
 }
 
 void