drm/i915: alloc intel_fb in the intel_fbdev struct

Allocate this struct instead, so we can re-use another allocated
elsewhere if needed.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[danvet: WARN_ON if there's no backing storage attached to an fb,
that's a bug.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 44067bc..4386faf 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -110,7 +110,7 @@
 
 struct intel_fbdev {
 	struct drm_fb_helper helper;
-	struct intel_framebuffer ifb;
+	struct intel_framebuffer *fb;
 	struct list_head fbdev_list;
 	struct drm_display_mode *our_mode;
 };