x86, acpi, tboot: Have a ACPI os prepare sleep instead of calling tboot_sleep.

The ACPI suspend path makes a call to tboot_sleep right before
it writes the PM1A, PM1B values. We replace the direct call to
tboot via an registration callback similar to __acpi_register_gsi.

CC: Len Brown <len.brown@intel.com>
Acked-by: Joseph Cihula <joseph.cihula@intel.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
[v1: Added __attribute__ ((unused))]
[v2: Introduced a wrapper instead of changing tboot_sleep return values]
[v3: Added return value AE_CTRL_SKIP for acpi_os_sleep_prepare]
Signed-off-by: Tang Liang <liang.tang@oracle.com>
[v1: Fix compile issues on IA64 and PPC64]
[v2: Fix where __acpi_os_prepare_sleep==NULL and did not go in sleep properly]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/acpi/acpica/hwsleep.c

@@ -43,9 +43,9 @@
  */
 
 #include <acpi/acpi.h>
+#include <linux/acpi.h>
 #include "accommon.h"
 #include "actables.h"
-#include <linux/tboot.h>
 #include <linux/module.h>
 
 #define _COMPONENT          ACPI_HARDWARE
@@ -344,8 +344,12 @@ acpi_status asmlinkage acpi_enter_sleep_state(u8 sleep_state)
 
 	ACPI_FLUSH_CPU_CACHE();
 
-	tboot_sleep(sleep_state, pm1a_control, pm1b_control);
-
+	status = acpi_os_prepare_sleep(sleep_state, pm1a_control,
+				       pm1b_control);
+	if (ACPI_SKIP(status))
+		return_ACPI_STATUS(AE_OK);
+	if (ACPI_FAILURE(status))
+		return_ACPI_STATUS(status);
 	/* Write #2: Write both SLP_TYP + SLP_EN */
 
 	status = acpi_hw_write_pm1_control(pm1a_control, pm1b_control);