cpuidle: calxeda: select ARM_CPU_SUSPEND

Like other ARM specific drivers, this one requires ARM_CPU_SUSPEND,
as shown by this linker error:

drivers/built-in.o: In function `calxeda_pwrdown_idle':
drivers/cpuidle/cpuidle-calxeda.c:84: undefined reference to `cpu_suspend'
drivers/cpuidle/cpuidle-calxeda.c:86: undefined reference to `cpu_resume'

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-pm@vger.kernel.org

drivers/cpuidle/Kconfig

@@ -36,6 +36,7 @@ if CPU_IDLE
 config CPU_IDLE_CALXEDA
 	bool "CPU Idle Driver for Calxeda processors"
 	depends on ARCH_HIGHBANK
+	select ARM_CPU_SUSPEND
 	help
 	  Select this to enable cpuidle on Calxeda processors.