interconnect: Add a common helper for removing all nodes

The removal of all nodes from a provider seem to be a common functionality
for all existing users and it would make sense to factor out this into a
a common helper function.

Suggested-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>