sh: Provide cpu_idle_wait() to fix up cpuidle/SMP build.

Crib the x86 cpu_idle_wait() implementation and shove it in with the
idle code, subsequently enabling ARCH_HAS_CPU_IDLE_WAIT.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/include/asm/system.h

@@ -154,6 +154,7 @@ extern struct dentry *sh_debugfs_root;
 
 void per_cpu_trap_init(void);
 void default_idle(void);
+void cpu_idle_wait(void);
 
 asmlinkage void break_point_trap(void);