cpuidle: kirkwood: Make kirkwood_cpuidle_remove function static

This local symbol is used only in this file.
Fix the following sparse warnings:

drivers/cpuidle/cpuidle-kirkwood.c:73:5: warning: symbol 'kirkwood_cpuidle_remove' was not declared. Should it be static ?
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/cpuidle/cpuidle-kirkwood.c

@@ -70,7 +70,7 @@ static int kirkwood_cpuidle_probe(struct platform_device *pdev)
 	return cpuidle_register(&kirkwood_idle_driver, NULL);
 }
 
-int kirkwood_cpuidle_remove(struct platform_device *pdev)
+static int kirkwood_cpuidle_remove(struct platform_device *pdev)
 {
 	cpuidle_unregister(&kirkwood_idle_driver);
 	return 0;