ACPI / PM: Fix build problems for !CONFIG_ACPI related to NVS rework

The recent rework of the NVS saving/restoring code introduced two
build issues for !CONFIG_ACPI, a warning in drivers/acpi/internal.h
and an error in arch/x86/kernel/e820.c.

Fix them by providing suitable static inline definitions of the
relevant functions.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/internal.h

diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 7c23b76..6d69bbed 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -90,7 +90,7 @@
 static inline int acpi_sleep_proc_init(void) { return 0; }
 static inline int suspend_nvs_alloc(void) { return 0; }
 static inline void suspend_nvs_free(void) {}
-static inline int suspend_nvs_save(void) {}
+static inline int suspend_nvs_save(void) { return 0; }
 static inline void suspend_nvs_restore(void) {}
 #endif