Compilation fix for ixgbe_main.c.

Under CONFIG_DCA the compilation is broken since the commit
bd0362dde080cef377d99fa5beb5c25308c29c73 (ixgbe: Add optional
DCA infrastructure).

IXGBE_SUCCESS is not defined anywhere, replace it with 0.

Signed-off-by: Denis V. Lunev <[e-mail]>
Signed-off-by: Jeff Garzik <[e-mail]>

drivers/net/ixgbe/ixgbe_main.c

···
 		/* Always use CB2 mode, difference is masked
 		 * in the CB driver. */
 		IXGBE_WRITE_REG(&adapter->hw, IXGBE_DCA_CTRL, 2);
-		if (dca_add_requester(dev) == IXGBE_SUCCESS) {
+		if (dca_add_requester(dev) == 0) {
 			ixgbe_setup_dca(adapter);
 			break;
 		}
···
 		break;
 	}
 
-	return IXGBE_SUCCESS;
+	return 0;
 }
 
 #endif /* CONFIG_DCA */
···
 		goto err_register;
 
 #ifdef CONFIG_DCA
-	if (dca_add_requester(&pdev->dev) == IXGBE_SUCCESS) {
+	if (dca_add_requester(&pdev->dev) == 0) {
 		adapter->flags |= IXGBE_FLAG_DCA_ENABLED;
 		/* always use CB2 mode, difference is masked
 		 * in the CB driver */