xen / ACPI: notify xen when reduced hardware sleep is available

Use the acpi_os_prepare_extended_sleep() callback to notify xen
to make use of the reduced hardware sleep functionality

The xen hypervisor change underlying this is commit 62d1a69
("ACPI: support v5 (reduced HW) sleep interface") on the master
branch of git://xenbits.xen.org/xen.git.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Ben Guthro <benjamin.guthro@citrix.com>
Acked-by: Konrad Wilk <konrad.wilk@oracle.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/include/xen/interface/platform.h b/include/xen/interface/platform.h
index c57d5f6..f1331e3 100644
--- a/include/xen/interface/platform.h
+++ b/include/xen/interface/platform.h
@@ -152,10 +152,11 @@
 #define XENPF_enter_acpi_sleep    51
 struct xenpf_enter_acpi_sleep {
 	/* IN variables */
-	uint16_t pm1a_cnt_val;      /* PM1a control value. */
-	uint16_t pm1b_cnt_val;      /* PM1b control value. */
+	uint16_t val_a;             /* PM1a control / sleep type A. */
+	uint16_t val_b;             /* PM1b control / sleep type B. */
 	uint32_t sleep_state;       /* Which state to enter (Sn). */
-	uint32_t flags;             /* Must be zero. */
+#define XENPF_ACPI_SLEEP_EXTENDED 0x00000001
+	uint32_t flags;             /* XENPF_ACPI_SLEEP_*. */
 };
 DEFINE_GUEST_HANDLE_STRUCT(xenpf_enter_acpi_sleep_t);