UHCI: don't stop at an Iso error

Unlike other sorts of endpoint queues, Isochronous queues don't stop
when an error is encountered.  This patch (as772) fixes the scanning
routine in uhci-hcd, to make it keep on going when it finds an Iso
error.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>