drm/omap: fix crash on module unload

When unloading omapdrm we get a NULL pointer deref in
omap_drm_irq_uninstall(). This is caused by:

967dd48417874dd25491a4e933648f394a64f70f ("drm: remove
drm_vblank_no_hw_counter assignment from driver code")

We shut down all the crtcs at unload time before calling
omap_drm_irq_uninstall, so the code in omap_drm_irq_uninstall() is
unnecessary and can be removed.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/gpu/drm/omapdrm/omap_irq.c

@@ -285,25 +285,11 @@ int omap_drm_irq_install(struct drm_device *dev)
 void omap_drm_irq_uninstall(struct drm_device *dev)
 {
 	struct omap_drm_private *priv = dev->dev_private;
-	unsigned long irqflags;
-	int i;
 
 	if (!dev->irq_enabled)
 		return;
 
 	dev->irq_enabled = false;
 
-	/* Wake up any waiters so they don't hang. */
-	if (dev->num_crtcs) {
-		spin_lock_irqsave(&dev->vbl_lock, irqflags);
-		for (i = 0; i < dev->num_crtcs; i++) {
-			wake_up(&dev->vblank[i].queue);
-			dev->vblank[i].enabled = false;
-			dev->vblank[i].last =
-				dev->driver->get_vblank_counter(dev, i);
-		}
-		spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
-	}
-
 	priv->dispc_ops->free_irq(dev);
 }