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
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 7183474..c494b79 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -803,7 +803,7 @@
 			entry->flags &= ~EXEC_OBJECT_NEEDS_FENCE;
 		need_fence =
 			entry->flags & EXEC_OBJECT_NEEDS_FENCE &&
-			obj->tiling_mode != I915_TILING_NONE;
+			i915_gem_object_is_tiled(obj);
 		need_mappable = need_fence || need_reloc_mappable(vma);
 
 		if (entry->flags & EXEC_OBJECT_PINNED)