greybus: Switch to Cport 0 for svc and control protocol

Initially we fixed it to Cport 2, but its changed to Cport 0 now. Lets
switch that in code as well.

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