drm/i915: Fixup global gtt cleanup

The global gtt is setup up in 2 parts, so we need to be careful
with the cleanup. For consistency shovel it all into the ->cleanup
callback, like with ppgtt.

Noticed because it blew up in the out_gtt: cleanup code while
fiddling with the vgacon code.

Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 931b906..41e864e 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -1985,7 +1985,10 @@
 
 	struct i915_gtt *gtt = container_of(vm, struct i915_gtt, base);
 
-	drm_mm_takedown(&vm->mm);
+	if (drm_mm_initialized(&vm->mm)) {
+		drm_mm_takedown(&vm->mm);
+		list_del(&vm->global_link);
+	}
 	iounmap(gtt->gsm);
 	teardown_scratch_page(vm->dev);
 }
@@ -2018,6 +2021,10 @@
 
 static void i915_gmch_remove(struct i915_address_space *vm)
 {
+	if (drm_mm_initialized(&vm->mm)) {
+		drm_mm_takedown(&vm->mm);
+		list_del(&vm->global_link);
+	}
 	intel_gmch_remove();
 }