ACPI: enable ACPI_PROCESSOR_IDLE on ARM64

Now that ACPI processor idle driver supports LPI(Low Power Idle), lets
enable ACPI_PROCESSOR_IDLE for ARM64 too.

This patch just removes the IA64 and X86 dependency on ACPI_PROCESSOR_IDLE
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/Kconfig

@@ -238,7 +238,7 @@ config ACPI_CPPC_LIB
 config ACPI_PROCESSOR
 	tristate "Processor"
 	depends on X86 || IA64 || ARM64
-	select ACPI_PROCESSOR_IDLE if X86 || IA64
+	select ACPI_PROCESSOR_IDLE
 	select ACPI_CPU_FREQ_PSS if X86 || IA64
 	default y
 	help