interruptible_sleep_on_locked() is just an open-coded
wait_event_interruptible_timeout(), with the one difference that
interruptible_sleep_on_locked() doesn't bother to check the condition on
which it is waiting, depending instead on the BKL to avoid the case
where it blocks after the wakeup has already been called.

locks_block_on_timeout() is only used in one place, so it's actually
simpler to inline it into its caller.
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>