greybus: svc: add route create operation

Implement the SVC Protocol Route Create Operation.

Tested-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Perry Hung <perry@leaflabs.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>