USB: EHCI: report actual_length for iso transfers

This patch (as1259b) makes ehci-hcd return the total number of bytes
transferred in urb->actual_length for Isochronous transfers.
Until now, the actual_length value was unaccountably left at 0.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>