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>
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a1c8f39..99589e7 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -290,6 +290,12 @@
 
 endmenu
 
+menu "CPU Power Management"
+
+source "drivers/cpuidle/Kconfig"
+
+endmenu
+
 source "net/Kconfig"
 
 source "drivers/Kconfig"