greybus: remove redundant latency-tag sanity checks

Core will never call host-device callbacks with invalid arguments (and
that would still need to be verified in bridge firmware anyway), so
remove the redundant and insufficient sanity check from the callbacks.

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