python-serial: allow to build with Python 3

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/python-serial/Config.in

@@ -1,6 +1,6 @@
 config BR2_PACKAGE_PYTHON_SERIAL
 	bool "python-serial"
-	depends on BR2_PACKAGE_PYTHON
+	depends on BR2_PACKAGE_PYTHON || BR2_PACKAGE_PYTHON3
 	help
 	  python-serial is a Python library to access serial ports.