[POWERPC] spufs: don't (ab)use SCHED_IDLE

commit 4ef11014 introduced a usage of SCHED_IDLE to detect when
a context is within spu_run.

Instead of SCHED_IDLE (which has other meaning), add a flag to
sched_flags to tell if a context should be running.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 5d5f680..00528ef 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -867,7 +867,7 @@
 	if (ctx->policy == SCHED_FIFO)
 		goto out;
 
-	if (--ctx->time_slice && ctx->policy != SCHED_IDLE)
+	if (--ctx->time_slice && test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
 		goto out;
 
 	spu = ctx->spu;
@@ -877,7 +877,7 @@
 	new = grab_runnable_context(ctx->prio + 1, spu->node);
 	if (new) {
 		spu_unschedule(spu, ctx);
-		if (ctx->policy != SCHED_IDLE)
+		if (test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
 			spu_add_to_rq(ctx);
 	} else {
 		spu_context_nospu_trace(spusched_tick__newslice, ctx);