arm64: add CPU power management menu/entries

This patch provides a menu for CPU power management options in the
arm64 Kconfig and adds an entry to enable the generic CPU idle configuration.
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

arch/arm64/Kconfig

@@ -290,6 +290,12 @@ config ARM64_CPU_SUSPEND
 
 endmenu
 
+menu "CPU Power Management"
+
+source "drivers/cpuidle/Kconfig"
+
+endmenu
+
 source "net/Kconfig"
 
 source "drivers/Kconfig"