ramips: fix ethernet driver tx completion polling

- budget is decremented with completed frames, so don't check if done is
smaller
- ACK the interrupt before processing further frames to fix a small race
condition.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 44234

target/linux/ramips/files/drivers/net/ethernet/ralink/ralink_soc_eth.c

@@ -902,11 +902,11 @@ txpoll_again:
 	if (!done)
 		return 0;
 
-	if (done < budget) {
+	if (budget) {
+		fe_reg_w32(tx_intr, FE_REG_FE_INT_STATUS);
 		hwidx = fe_reg_r32(FE_REG_TX_DTX_IDX0);
 		if (idx != hwidx)
 			goto txpoll_again;
-		fe_reg_w32(tx_intr, FE_REG_FE_INT_STATUS);
 	}
 
 	netdev_completed_queue(netdev, done, bytes_compl);