greybus: s/bundle_cport_id/intf_cport_id

This isn't unique just for the bundle but the complete interface. Its
wrong to call it bundle_cport_id. Lets name it intf_cport_id to make
things clear.

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