drm/irq: Coding style fix

Noticed by Thierry Reding in his review, but I've merged the drm
vblank rework topic branch a bit too quickly. So separate fixup.

Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_irq.c

@@ -887,7 +887,8 @@ static int drm_vblank_enable(struct drm_device *dev, int crtc)
 	spin_lock(&dev->vblank_time_lock);
 
 	if (!dev->vblank[crtc].enabled) {
-		/* Enable vblank irqs under vblank_time_lock protection.
+		/*
+		 * Enable vblank irqs under vblank_time_lock protection.
 		 * All vblank count & timestamp updates are held off
 		 * until we are done reinitializing master counter and
 		 * timestamps. Filtercode in drm_handle_vblank() will