drm/i915: Remove use on gma_bus_addr on gen6+

We have enough info to not use the intel_gtt bridge stuff.

v2: Move setup of mappable_base above the legacy init stuff because we
still need that on older platforms. (Daniel)

v3: Remove the dev_priv hunk which was rebased in by accident

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com> (v2)
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 59e0269..ce1d074 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1203,7 +1203,7 @@
 		goto err_unpin;
 
 	ring->virtual_start =
-		ioremap_wc(dev_priv->mm.gtt->gma_bus_addr + obj->gtt_offset,
+		ioremap_wc(dev_priv->gtt.mappable_base + obj->gtt_offset,
 			   ring->size);
 	if (ring->virtual_start == NULL) {
 		DRM_ERROR("Failed to map ringbuffer.\n");