network drivers: sparse warning fixes

Fix some of the easy warnings in network device drivers.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/e100.c b/drivers/net/e100.c
index 7bd9604..64f35e2 100644
--- a/drivers/net/e100.c
+++ b/drivers/net/e100.c
@@ -1990,7 +1990,7 @@
 {
 	struct nic *nic = container_of(napi, struct nic, napi);
 	struct net_device *netdev = nic->netdev;
-	int work_done = 0;
+	unsigned int work_done = 0;
 	int tx_cleaned;
 
 	e100_rx_clean(nic, &work_done, budget);