USB: OHCI: Don't mark EDs as ED_OPER if scheduling fails

USB: OHCI: Don't mark EDs as ED_OPER if scheduling fails

Since ed_schedule begins with marking the ED as "operational",
the ED may be left in such state even if scheduling actually
fails.

This allows future submission attempts to smuggle this ED to the
hardware behind the scheduler's back and without linking it to
the ohci->eds_in_use list.

The former causes bandwidth saturation and data loss on isoc
endpoints, the latter crashes the kernel when attempt is made
to unlink such ED from this list.

Fix ed_schedule to update ED state only on successful return.

Signed-off-by: Michal Pecio <michal.pecio@gmail.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>