mmc: sdhci-pci: add runtime pm support

Ths patch allows runtime PM for sdhci-pci, runtime suspending after
inactivity of 50ms and ensuring runtime resume before SDHC registers
are accessed.  During runtime suspend, interrupts are masked.
The host controller state is restored at runtime resume.

For Medfield, the host controller's card detect mechanism is
supplanted by an always-on GPIO which provides for card detect wake-up.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 7bd919c..0a5b654 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -379,4 +379,9 @@
 extern void sdhci_enable_irq_wakeups(struct sdhci_host *host);
 #endif
 
+#ifdef CONFIG_PM_RUNTIME
+extern int sdhci_runtime_suspend_host(struct sdhci_host *host);
+extern int sdhci_runtime_resume_host(struct sdhci_host *host);
+#endif
+
 #endif /* __SDHCI_HW_H */