idle: Implement generic idle function

All idle functions in arch/* are more or less the same, plus minus a
few bugs and extra instrumentation, tickless support and other
optional items.

Implement a generic idle function which resembles the functionality
found in arch/. Provide weak arch_cpu_idle_* functions which can be
overridden by the architecture code if needed.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130321215233.646635455@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 7419e30..c6f6e08 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -220,4 +220,12 @@
 void cpu_startup_entry(enum cpuhp_state state);
 void cpu_idle(void);
 
+void cpu_idle_poll_ctrl(bool enable);
+
+void arch_cpu_idle(void);
+void arch_cpu_idle_prepare(void);
+void arch_cpu_idle_enter(void);
+void arch_cpu_idle_exit(void);
+void arch_cpu_idle_dead(void);
+
 #endif /* _LINUX_CPU_H_ */