cpuidle / kirkwood: remove redundant Kconfig option

When the CPU_IDLE and the ARCH_KIRKWOOD options are set it is
pointless to define a new option CPU_IDLE_KIRKWOOD because it
is redundant.

The Makefile drivers directory contains a condition to compile
the cpuidle drivers:

obj-$(CONFIG_CPU_IDLE)          += cpuidle/

Hence, if CPU_IDLE is not set we won't enter this directory.

This patch removes the useless Kconfig option and replaces the
condition in the Makefile by CONFIG_ARCH_KIRKWOOD.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
index 24c6e7d..0d8bd55 100644
--- a/drivers/cpuidle/Makefile
+++ b/drivers/cpuidle/Makefile
@@ -6,4 +6,4 @@
 obj-$(CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED) += coupled.o
 
 obj-$(CONFIG_CPU_IDLE_CALXEDA) += cpuidle-calxeda.o
-obj-$(CONFIG_CPU_IDLE_KIRKWOOD) += cpuidle-kirkwood.o
+obj-$(CONFIG_ARCH_KIRKWOOD) += cpuidle-kirkwood.o