[forcedeth] Exit poll() as early as possible if no work to do

Signed-off-by: Thomas Miletich <thomas.miletich@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/forcedeth.c

 
 	status = readl ( ioaddr + NvRegIrqStatus ) & NVREG_IRQSTAT_MASK;
 
+	/* Return when no interrupts have been triggered */
+	if ( ! status )
+		return;
+
 	/* Clear interrupts */
 	writel ( NVREG_IRQSTAT_MASK, ioaddr + NvRegIrqStatus );
 
 	if ( ( status & NVREG_IRQ_LINK ) || ! ( netdev_link_ok ( netdev ) ) )
 		forcedeth_link_status ( netdev );
 
-	/* Return when no interrupts have been triggered */
-	if ( ! status )
-		return;
-
 	/* Process transmitted packets */
 	nv_process_tx_packets ( netdev );