fix block leak

Notes:
Mon Oct 6 15:18:20 EDT 2008 geoff
    done differently


Reference: /n/sources/patch/applied/usberrleak
Date: Mon Oct  6 01:45:26 CES 2008
Signed-off-by: quanstro@quanstro.net
Reviewed-by: geoff

--- /sys/src/9/pc/usbohci.c	Mon Oct  6 01:45:20 2008
+++ /sys/src/9/pc/usbohci.c	Mon Oct  6 01:45:16 2008
@@ -2042,8 +2042,10 @@
 		dcclean(b->rp, m);
 		if(ep->epmode == Isomode && ep->buffered <= ep->bw<<1){
 			sleep(&ep->dir[Dirout].rend, weptdone, ep);
-			if(ep->dir[Dirout].err)
+			if(ep->dir[Dirout].err){
+				freeb(b);
 				error(ep->dir[Dirout].err);
+			}
 		}
 		while(m > 0){
 			int l;