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: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NGraeme Gregory <graeme.gregory@linaro.org>
Signed-off-by: NTomasz Nowicki <tomasz.nowicki@linaro.org>
Signed-off-by: NHanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>