[ARM SMP] Track CPU idle threads

Track the idle thread task_struct for each CPU.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/include/asm-arm/cpu.h b/include/asm-arm/cpu.h
index fcbdd40..751bc74 100644
--- a/include/asm-arm/cpu.h
+++ b/include/asm-arm/cpu.h
@@ -16,6 +16,7 @@
 struct cpuinfo_arm {
 	struct cpu	cpu;
 #ifdef CONFIG_SMP
+	struct task_struct *idle;
 	unsigned int	loops_per_jiffy;
 #endif
 };