If a driver uses DPM_FLAG_SMART_SUSPEND and the device is already
runtime suspended when hibernate is started PCI core skips runtime
resuming the device but still clears pci_dev->state_saved. After the
hibernation image is written pci_pm_thaw_noirq() makes sure subsequent
thaw phases for the device are also skipped leaving it runtime suspended
with pci_dev->state_saved == false.

When the device is eventually runtime resumed pci_pm_runtime_resume()
restores config space by calling pci_restore_standard_config(), however
because pci_dev->state_saved == false pci_restore_state() never actually
restores the config space leaving the device in a state that is not what
the driver might expect.

For example here is what happens for intel-lpss I2C devices once the
hibernation snapshot is taken:

  intel-lpss 0000:00:15.0: power state changed by ACPI to D0
  intel-lpss 0000:00:1e.0: power state changed by ACPI to D3cold
  video LNXVIDEO:00: Restoring backlight state
  PM: hibernation exit
  i2c_designware i2c_designware.1: Unknown Synopsys component type: 0xffffffff
  i2c_designware i2c_designware.0: Unknown Synopsys component type: 0xffffffff
  i2c_designware i2c_designware.1: timeout in disabling adapter
  i2c_designware i2c_designware.0: timeout in disabling adapter

Since PCI config space is not restored the device is still in D3hot
making MMIO register reads return 0xffffffff.

Fix this by clearing pci_dev->state_saved only if we actually end up
runtime resuming the device.

Fixes: c4b65157 (PCI / PM: Take SMART_SUSPEND driver flag into account)
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: 4.15+ <stable@vger.kernel.org> # 4.15+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>