drm/i915: stop using dev->agp->base

For that to work we need to export the base address of the gtt
mmio window from intel-gtt. Also replace all other uses of
dev->agp by values we already have at hand.

Reviewed-by: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_fb.c b/drivers/gpu/drm/i915/intel_fb.c
index bf86907..e9f8338 100644
--- a/drivers/gpu/drm/i915/intel_fb.c
+++ b/drivers/gpu/drm/i915/intel_fb.c
@@ -140,7 +140,9 @@
 	info->fix.smem_start = dev->mode_config.fb_base + obj->gtt_offset;
 	info->fix.smem_len = size;
 
-	info->screen_base = ioremap_wc(dev->agp->base + obj->gtt_offset, size);
+	info->screen_base =
+		ioremap_wc(dev_priv->mm.gtt_base_addr + obj->gtt_offset,
+			   size);
 	if (!info->screen_base) {
 		ret = -ENOSPC;
 		goto out_unpin;