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/include/drm/drmP.h b/include/drm/drmP.h
index 8e8c392..7a7cfe8 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1353,7 +1353,7 @@
 				/* IRQ support (drm_irq.h) */
 extern int drm_control(struct drm_device *dev, void *data,
 		       struct drm_file *file_priv);
-extern int drm_irq_install(struct drm_device *dev);
+extern int drm_irq_install(struct drm_device *dev, int irq);
 extern int drm_irq_uninstall(struct drm_device *dev);
 
 extern int drm_vblank_init(struct drm_device *dev, int num_crtcs);