sched: clarify commment for TS_POLLING

TS_POLLING set tells the scheduler an idle_task will poll
need_resched() to look for work.

TS_POLLING clear tells resched_task() and wake_up_idle_cpu()
that the remote CPU's idle_task is now sleeping in idle,
and thus requires a reschedule interrupt notice work.

Update the description of TS_POLLING to reflect how it works.
"idle task polling need_resched, skip sending interrupt"

Wordsmithing-by: Milton Miller <[e-mail]>
Signed-off-by: Len Brown <[e-mail]>
Acked-by: Peter Zijlstra <[e-mail]>

arch/x86/include/asm/thread_info.h

···
 #define TS_USEDFPU		0x0001	/* FPU was used by this task
 					   this quantum (SMP) */
 #define TS_COMPAT		0x0002	/* 32bit syscall active (64BIT)*/
-#define TS_POLLING		0x0004	/* true if in idle loop
-					   and not sleeping */
+#define TS_POLLING		0x0004	/* idle task polling need_resched,
+					   skip sending interrupt */
 #define TS_RESTORE_SIGMASK	0x0008	/* restore signal mask in do_signal() */
 #define TS_XSAVE		0x0010	/* Use xsave/xrstor */