x86/platform/intel-mid: Retrofit pci_platform_pm_ops ->get_state hook

Commit cc7cc02bada8 ("PCI: Query platform firmware for device power
state") augmented struct pci_platform_pm_ops with a ->get_state hook and
implemented it for acpi_pci_platform_pm, the only pci_platform_pm_ops
existing till v4.7.

However v4.8 introduced another pci_platform_pm_ops for Intel Mobile
Internet Devices with commit 5823d0893ec2 ("x86/platform/intel-mid: Add
Power Management Unit driver").  It is missing the ->get_state hook,
which is fatal since pci_set_platform_pm() enforces its presence.  Andy
Shevchenko reports that without the present commit, such a device
"crashes without even a character printed out on serial console and
reboots (since watchdog)".

Retrofit mid_pci_platform_pm with the missing callback to fix the
breakage.

Acked-and-tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Fixes: cc7cc02bada8 ("PCI: Query platform firmware for device power state")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: http://lkml.kernel.org/r/7c1567d4c49303a4aada94ba16275cbf56b8976b.1477221514.git.lukas@wunner.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/drivers/pci/pci-mid.c b/drivers/pci/pci-mid.c
index 55f453d..c7f3408 100644
--- a/drivers/pci/pci-mid.c
+++ b/drivers/pci/pci-mid.c
@@ -29,6 +29,11 @@
 	return intel_mid_pci_set_power_state(pdev, state);
 }
 
+static pci_power_t mid_pci_get_power_state(struct pci_dev *pdev)
+{
+	return intel_mid_pci_get_power_state(pdev);
+}
+
 static pci_power_t mid_pci_choose_state(struct pci_dev *pdev)
 {
 	return PCI_D3hot;
@@ -52,6 +57,7 @@
 static struct pci_platform_pm_ops mid_pci_platform_pm = {
 	.is_manageable	= mid_pci_power_manageable,
 	.set_state	= mid_pci_set_power_state,
+	.get_state	= mid_pci_get_power_state,
 	.choose_state	= mid_pci_choose_state,
 	.sleep_wake	= mid_pci_sleep_wake,
 	.run_wake	= mid_pci_run_wake,