the uncontroversal gcc 4.0 compilation fixes

src/drivers/net/natsemi.c

 		 const char  *p)     /* Packet */
 {
     u32 to, nstype;
-    u32 tx_status;
+    volatile u32 tx_status;
     
     /* Stop the transmitter */
     outl(TxOff, ioaddr + ChipCmd);
 
     to = currticks() + TX_TIMEOUT;
 
-    while ((((volatile u32) tx_status=txd.cmdsts) & OWN) && (currticks() < to))
+    while (((tx_status=txd.cmdsts) & OWN) && (currticks() < to))
         /* wait */ ;
 
     if (currticks() >= to) {

src/drivers/net/sis900.c

                 const char  *p)     /* Packet */
 {
     u32 to, nstype;
-    u32 tx_status;
+    volatile u32 tx_status;
     
     /* Stop the transmitter */
     outl(TxDIS | inl(ioaddr + cr), ioaddr + cr);
 
     to = currticks() + TX_TIMEOUT;
 
-    while ((((volatile u32) tx_status=txd.cmdsts) & OWN) && (currticks() < to))
+    while (((tx_status=txd.cmdsts) & OWN) && (currticks() < to))
         /* wait */ ;
 
     if (currticks() >= to) {