greybus: fix request timeout bug

greybus: fix request timeout bug

This commit changed the timeout behavior for operations:
    6a8732e operation: make the timeout a per-operation thing...

It unfortunately left in place some code that was only
appropriate for per-connection timeouts.  In particular,
the timer for an operation is currently getting started
only if no existing operations are in flight.

Fix that oversight, and schedule an operation's timer
unconditionally.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>