sc92031: add a link to the datasheet

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/sc92031.c

@@ -13,6 +13,9 @@
  *  Both are almost identical and seem to be based on pci-skeleton.c
  *
  *  Rewritten for 2.6 by Cesar Eduardo Barros
+ *
+ *  A datasheet for this chip can be found at
+ *  http://www.silan.com.cn/english/products/pdf/SC92031AY.pdf
  */
 
 /* Note about set_mac_address: I don't know how to change the hardware