greybus: svc: don't trust any struct devices

As the svc code is "odd" in how things are set up at initial connection
time, we can't always "know" that we have a valid bundle to use for
error messages.  So just punt and always use pr_*() calls to ensure that
we never incorrectly dereference a pointer.

This will get fixed up soon, but for now, let's just live with a bit
messier error messages in the log.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>