PM: sleep: Use DPM_FLAG_SMART_SUSPEND conditionally

PM: sleep: Use DPM_FLAG_SMART_SUSPEND conditionally

A recent discussion has revealed that using DPM_FLAG_SMART_SUSPEND
unconditionally is generally problematic because it may lead to
situations in which the device's runtime PM information is internally
inconsistent or does not reflect its real state [1].

For this reason, change the handling of DPM_FLAG_SMART_SUSPEND so that
it is only taken into account if it is consistently set by the drivers
of all devices having any PM callbacks throughout dependency graphs in
accordance with the following rules:

 - The "smart suspend" feature is only enabled for devices whose drivers
   ask for it (that is, set DPM_FLAG_SMART_SUSPEND) and for devices
   without PM callbacks unless they have never had runtime PM enabled.

 - The "smart suspend" feature is not enabled for a device if it has not
   been enabled for the device's parent unless the parent does not take
   children into account or it has never had runtime PM enabled.

 - The "smart suspend" feature is not enabled for a device if it has not
   been enabled for one of the device's suppliers taking runtime PM into
   account unless that supplier has never had runtime PM enabled.

Namely, introduce a new device PM flag called smart_suspend that is only
set if the above conditions are met and update all DPM_FLAG_SMART_SUSPEND
users to check power.smart_suspend instead of directly checking the
latter.

At the same time, drop the power.set_active flage introduced recently
in commit 3775fc538f53 ("PM: sleep: core: Synchronize runtime PM status
of parents and children") because it is now sufficient to check
power.smart_suspend along with the dev_pm_skip_resume() return value
to decide whether or not pm_runtime_set_active() needs to be called
for the device.

Link: https://lore.kernel.org/linux-pm/CAPDyKFroyU3YDSfw_Y6k3giVfajg3NQGwNWeteJWqpW29BojhQ@mail.gmail.com/
Fixes: 7585946243d6 ("PM: sleep: core: Restrict power.set_active propagation")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com> # drivers/pci
Link: https://patch.msgid.link/1914558.tdWV9SEqCh@rjwysocki.net