drm/i915: Repack fence tiling mode and stride into a single integer

In the previous commit, we moved the obj->tiling_mode out of a bitfield
and into its own integer so that we could safely use READ_ONCE(). Let us
now repair some of that damage by sharing the tiling_mode with its
companion, the fence stride.

v2: New magic

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-18-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_fbc.c

@@ -741,7 +741,7 @@ static void intel_fbc_update_state_cache(struct intel_crtc *crtc,
 	cache->fb.pixel_format = fb->pixel_format;
 	cache->fb.stride = fb->pitches[0];
 	cache->fb.fence_reg = obj->fence_reg;
-	cache->fb.tiling_mode = obj->tiling_mode;
+	cache->fb.tiling_mode = i915_gem_object_get_tiling(obj);
 }
 
 static bool intel_fbc_can_activate(struct intel_crtc *crtc)