drm: pass the irq explicitly to drm_irq_install

Unfortunately this requires a drm-wide change, and I didn't see a sane
way around that. Luckily it's fairly simple, we just need to inline
the respective get_irq implementation from either drm_pci.c or
drm_platform.c.

With that we can now also remove drm_dev_to_irq from drm_irq.c.

Reviewed-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d2cc19a..a94938f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4523,7 +4523,7 @@
 
 	BUG_ON(!list_empty(&dev_priv->gtt.base.active_list));
 
-	ret = drm_irq_install(dev);
+	ret = drm_irq_install(dev, dev->pdev->irq);
 	if (ret)
 		goto cleanup_ringbuffer;
 	mutex_unlock(&dev->struct_mutex);