ACPI / sleep: Introduce CONFIG_ACPI_SYSTEM_POWER_STATES_SUPPORT

ACPI 5.1 does not currently support S states for ARM64 hardware but
ACPI code will call acpi_target_system_state() and acpi_sleep_init()
for device power management, so introduce
CONFIG_ACPI_SYSTEM_POWER_STATES_SUPPORT and select it for x86 and
ia64 only to make sleep functions available, and also introduce stub
function to allow other drivers to function until S states are defined
for ARM64.

It will be no functional change for x86 and IA64.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Graeme Gregory <graeme.gregory@linaro.org>
Signed-off-by: Tomasz Nowicki <tomasz.nowicki@linaro.org>
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 074e52b..cc3414f 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -10,6 +10,7 @@
 	select ARCH_MIGHT_HAVE_PC_SERIO
 	select PCI if (!IA64_HP_SIM)
 	select ACPI if (!IA64_HP_SIM)
+	select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
 	select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
 	select HAVE_UNSTABLE_SCHED_CLOCK
 	select HAVE_IDE