interconnect: Add helpers for enabling/disabling a path

[ Upstream commit 7d374b20908338c9fbb03ea8022a11f3b3e0e55f ]

There is a repeated pattern in multiple drivers where they want to switch
the bandwidth between zero and some other value. This is happening often
in the suspend/resume callbacks. Let's add helper functions to enable and
disable the path, so that callers don't have to take care of remembering
the bandwidth values and handle this in the framework instead.

With this patch the users can call icc_disable() and icc_enable() to lower
their bandwidth request to zero and then restore it back to it's previous
value.

Suggested-by: Evan Green <evgreen@chromium.org>
Suggested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Link: https://lore.kernel.org/r/20200507120846.8354-1-georgi.djakov@linaro.org


Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Stable-dep-of: d2d69354226d ("USB: dwc3: qcom: fix NULL-deref on suspend")
Signed-off-by: Sasha Levin <sashal@kernel.org>