net/fsl_pq_mdio: add module license GPL

or it will taint the kernel and fail to load becuase
of_address_to_resource() is GPL only.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/fsl_pq_mdio.c

@@ -427,3 +427,4 @@ void fsl_pq_mdio_exit(void)
 	of_unregister_platform_driver(&fsl_pq_mdio_driver);
 }
 module_exit(fsl_pq_mdio_exit);
+MODULE_LICENSE("GPL");