libata-acpi: add ACPI _PSx method

ACPI spec (ver 3.0a, p289) requires IDE power on/off executes ACPI _PSx
methods. As recently most PATA drivers use libata, this patch adds _PSx
method support in libata. ACPI spec doesn't mention if SATA requires the
same _PSx method.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
index 048e26c..8cf0874 100644
--- a/drivers/ata/libata.h
+++ b/drivers/ata/libata.h
@@ -114,6 +114,7 @@
 extern void ata_acpi_on_resume(struct ata_port *ap);
 extern int ata_acpi_on_devcfg(struct ata_device *dev);
 extern void ata_acpi_on_disable(struct ata_device *dev);
+extern void ata_acpi_set_state(struct ata_port *ap, pm_message_t state);
 #else
 static inline void ata_acpi_associate_sata_port(struct ata_port *ap) { }
 static inline void ata_acpi_associate(struct ata_host *host) { }
@@ -122,6 +123,8 @@
 static inline void ata_acpi_on_resume(struct ata_port *ap) { }
 static inline int ata_acpi_on_devcfg(struct ata_device *dev) { return 0; }
 static inline void ata_acpi_on_disable(struct ata_device *dev) { }
+static inline void ata_acpi_set_state(struct ata_port *ap,
+				      pm_message_t state) { }
 #endif
 
 /* libata-scsi.c */