z85230: Fix FIFO handling

We must exit immediately on a FIFO fill not take the end of packet path
otherwise each underrun in PIO transmit mode causes a runt packet and the
data is lost.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/wan/z85230.c

@@ -407,7 +407,7 @@ static void z8530_tx(struct z8530_channel *c)
 	while(c->txcount) {
 		/* FIFO full ? */
 		if(!(read_zsreg(c, R0)&4))
-			break;
+			return;
 		c->txcount--;
 		/*
 		 *	Shovel out the byte