net: ipa: manage endpoints separate from clock

Currently, when (before) the last IPA clock reference is dropped,
all endpoints are suspended.  And whenever the first IPA clock
reference is taken, all endpoints are resumed (or started).

In most cases there's no need to start endpoints when the clock
starts.  So move the calls to ipa_endpoint_suspend() and
ipa_endpoint_resume() out of ipa_clock_put() and ipa_clock_get(),
respectiely.  Instead, only suspend endpoints when handling a system
suspend, and only resume endpoints when handling a system resume.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>