net: hip04: add missing MODULE_LICENSE

The hip04 ethernet driver causes a new compile-time warning
when built as a loadable module:

WARNING: modpost: missing MODULE_LICENSE() in drivers/net/ethernet/hisilicon/hip04_eth.o
see include/linux/module.h for more information

This adds the license as "GPL", which matches the header of the file.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hip04_eth.c

@@ -968,3 +968,4 @@ static struct platform_driver hip04_mac_driver = {
 module_platform_driver(hip04_mac_driver);
 
 MODULE_DESCRIPTION("HISILICON P04 Ethernet driver");
+MODULE_LICENSE("GPL");