MIPS: include cpuidle Kconfig menu

This patch simply includes the cpuidle Kconfig entries in preparation
for cpuidle drivers used on MIPS systems.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>

arch/mips/Kconfig

@@ -2678,12 +2678,16 @@ endmenu
 config MIPS_EXTERNAL_TIMER
 	bool
 
-if CPU_SUPPORTS_CPUFREQ && MIPS_EXTERNAL_TIMER
 menu "CPU Power Management"
+
+if CPU_SUPPORTS_CPUFREQ && MIPS_EXTERNAL_TIMER
 source "drivers/cpufreq/Kconfig"
-endmenu
 endif
 
+source "drivers/cpuidle/Kconfig"
+
+endmenu
+
 source "net/Kconfig"
 
 source "drivers/Kconfig"