sky2: reduce default Tx ring size

The default Tx ring size for the sky2 driver is quite large and could
cause excess buffer bloat for many users. The minimum ring size
possible and still allow handling  the worst case packet on 64bit platforms
is 38 which gets rounded up to a power of 2. But most packets only require
a couple of ring elements.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/sky2.c

@@ -68,7 +68,7 @@
 #define MAX_SKB_TX_LE	(2 + (sizeof(dma_addr_t)/sizeof(u32))*(MAX_SKB_FRAGS+1))
 #define TX_MIN_PENDING		(MAX_SKB_TX_LE+1)
 #define TX_MAX_PENDING		1024
-#define TX_DEF_PENDING		127
+#define TX_DEF_PENDING		63
 
 #define TX_WATCHDOG		(5 * HZ)
 #define NAPI_WEIGHT		64