[drivers] Fix warnings identified by gcc 4.5

In building gpxe for openSUSE Factory (part of kvm package), there were
a few problems identified by the compiler.  This patch addresses them.

Signed-off-by: Bruce Rogers <brogers@novell.com>
Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Marty Connor <mdc@etherboot.org>

src/drivers/net/ath5k/ath5k_qcu.c

 		}
 
 		if (tq->tqi_ready_time &&
-		(tq->tqi_type != AR5K_TX_QUEUE_ID_CAB))
+		(tq->tqi_type != AR5K_TX_QUEUE_CAB))
 			ath5k_hw_reg_write(ah, AR5K_REG_SM(tq->tqi_ready_time,
 				AR5K_QCU_RDYTIMECFG_INTVAL) |
 				AR5K_QCU_RDYTIMECFG_ENABLE,

src/drivers/net/ns83820.c

 	//			rx_ring[entry].link = 0;
 	rx_ring[entry].cmdsts = cpu_to_le32(CMDSTS_OWN);
 
-	ns->cur_rx = ++ns->cur_rx % NR_RX_DESC;
+	ns->cur_rx = (ns->cur_rx + 1) % NR_RX_DESC;
 
 	if (ns->cur_rx == 0)	/* We have wrapped the ring */
 	  kick_rx();

src/drivers/net/tulip.c

     if (rx_ring[tp->cur_rx].status & 0x00008000) {
 	/* return the descriptor and buffer to receive ring */
         rx_ring[tp->cur_rx].status = 0x80000000;
-	tp->cur_rx = (++tp->cur_rx) % RX_RING_SIZE;
+	tp->cur_rx = (tp->cur_rx + 1) % RX_RING_SIZE;
         return 0;
     }
 
 
     /* return the descriptor and buffer to receive ring */
     rx_ring[tp->cur_rx].status = 0x80000000;
-    tp->cur_rx = (++tp->cur_rx) % RX_RING_SIZE;
+    tp->cur_rx = (tp->cur_rx + 1) % RX_RING_SIZE;
 
     return 1;
 }