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_display.c b/drivers/gpu/drm/i915/intel_display.c
index 807e815..ac0f6b5 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7769,11 +7769,11 @@
 	if (dev_priv->fbdev == NULL)
 		return NULL;
 
-	obj = dev_priv->fbdev->ifb.obj;
+	obj = dev_priv->fbdev->fb->obj;
 	if (obj == NULL)
 		return NULL;
 
-	fb = &dev_priv->fbdev->ifb.base;
+	fb = &dev_priv->fbdev->fb->base;
 	if (fb->pitches[0] < intel_framebuffer_pitch_for_width(mode->hdisplay,
 							       fb->bits_per_pixel))
 		return NULL;