drm/vmwgfx/ttm_object: Reorder header to immediately precede its struct

Also add missing description for 'refcount'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/vmwgfx/ttm_object.c:60: error: Cannot parse struct or union!

Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: Zack Rusin <zackr@vmware.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Rob Clark <rob.clark@linaro.org>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115181601.3432599-30-lee.jones@linaro.org

drivers/gpu/drm/vmwgfx/ttm_object.c

@@ -42,6 +42,14 @@
  */
 
 
+#define pr_fmt(fmt) "[TTM] " fmt
+
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/atomic.h>
+#include "ttm_object.h"
+
 /**
  * struct ttm_object_file
  *
@@ -55,16 +63,9 @@
  *
  * @ref_hash: Hash tables of ref objects, one per ttm_ref_type,
  * for fast lookup of ref objects given a base object.
+ *
+ * @refcount: reference/usage count
  */
-
-#define pr_fmt(fmt) "[TTM] " fmt
-
-#include <linux/list.h>
-#include <linux/spinlock.h>
-#include <linux/slab.h>
-#include <linux/atomic.h>
-#include "ttm_object.h"
-
 struct ttm_object_file {
 	struct ttm_object_device *tdev;
 	spinlock_t lock;