net: cs89x0: add MODULE_LICENSE

This driver lacks a MODULE_LICENSE tag, leading to a Kbuild warning:

WARNING: modpost: missing MODULE_LICENSE() in drivers/net/ethernet/cirrus/cs89x0.o

This adds license, author, and description according to the
comment block at the start of the file.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cirrus/cs89x0.c

@@ -1913,3 +1913,7 @@ static struct platform_driver cs89x0_driver = {
 module_platform_driver_probe(cs89x0_driver, cs89x0_platform_probe);
 
 #endif /* CONFIG_CS89x0_PLATFORM */
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Crystal Semiconductor (Now Cirrus Logic) CS89[02]0 network driver");
+MODULE_AUTHOR("Russell Nelson <nelson@crynwr.com>");