sky2: advertising register 16 bits

The advertising bits (from ethtool.h) fit in 16 bits.

drivers/net/sky2.h

diff --git a/drivers/net/sky2.h b/drivers/net/sky2.h
index 43d2acc..0a8d821 100644
--- a/drivers/net/sky2.h
+++ b/drivers/net/sky2.h
@@ -1860,7 +1860,7 @@
 
 	dma_addr_t	     rx_le_map;
 	dma_addr_t	     tx_le_map;
-	u32		     advertising;	/* ADVERTISED_ bits */
+	u16		     advertising;	/* ADVERTISED_ bits */
 	u16		     speed;	/* SPEED_1000, SPEED_100, ... */
 	u8		     autoneg;	/* AUTONEG_ENABLE, AUTONEG_DISABLE */
 	u8		     duplex;	/* DUPLEX_HALF, DUPLEX_FULL */