[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/run.c b/arch/powerpc/platforms/cell/spufs/run.c
index 6221968..cac69e1 100644
--- a/arch/powerpc/platforms/cell/spufs/run.c
+++ b/arch/powerpc/platforms/cell/spufs/run.c
@@ -220,6 +220,7 @@
 		}
 	}
 
+	set_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags);
 	return 0;
 }
 
@@ -234,7 +235,7 @@
 	*npc = ctx->ops->npc_read(ctx);
 
 	spuctx_switch_state(ctx, SPU_UTIL_IDLE_LOADED);
-	ctx->policy = SCHED_IDLE;
+	clear_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags);
 	spu_release(ctx);
 
 	if (signal_pending(current))