spidernet: turn off descriptor chain end interrupt.

At some point, the transmit descriptor chain end interrupt (TXDCEINT)
was turned on. This is a mistake; and it damages small packet
transmit performance, as it results in a huge storm of interrupts.
Turn it off.
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/spider_net.h

@@ -222,6 +222,7 @@ extern char spider_net_driver_name[];
 #define SPIDER_NET_GDTBSTA             0x00000300
 #define SPIDER_NET_GDTDCEIDIS          0x00000002
 #define SPIDER_NET_DMA_TX_VALUE        SPIDER_NET_TX_DMA_EN | \
+                                       SPIDER_NET_GDTDCEIDIS | \
                                        SPIDER_NET_GDTBSTA
 
 #define SPIDER_NET_DMA_TX_FEND_VALUE	0x00030003
@@ -332,8 +333,7 @@ enum spider_net_int2_status {
 	SPIDER_NET_GRISPDNGINT
 };
 
-#define SPIDER_NET_TXINT	( (1 << SPIDER_NET_GDTFDCINT) | \
-                             (1 << SPIDER_NET_GDTDCEINT) )
+#define SPIDER_NET_TXINT	(1 << SPIDER_NET_GDTFDCINT)
 
 /* We rely on flagged descriptor interrupts */
 #define SPIDER_NET_RXINT	( (1 << SPIDER_NET_GDAFDCINT) )