nouveau: drop interrupt busy setting.

This causes problems with never going busy due to ptherm polling,
and after talking to Ben I can't see it being required.
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/nouveau/core/subdev/mc/base.c

@@ -30,7 +30,6 @@ nouveau_mc_intr(int irq, void *arg)
 {
 	struct nouveau_mc *pmc = arg;
 	const struct nouveau_mc_intr *map = pmc->intr_map;
-	struct nouveau_device *device = nv_device(pmc);
 	struct nouveau_subdev *unit;
 	u32 stat, intr;
 
@@ -54,8 +53,6 @@ nouveau_mc_intr(int irq, void *arg)
 		nv_error(pmc, "unknown intr 0x%08x\n", stat);
 	}
 
-	if (stat == IRQ_HANDLED)
-		pm_runtime_mark_last_busy(&device->pdev->dev);
 	return stat ? IRQ_HANDLED : IRQ_NONE;
 }