drm/i915/gvt: add the missing mdev attribute "name"

drm/i915/gvt: add the missing mdev attribute "name"

The mdev attribute "name" is required by some middle software, e.g.
KubeVirt, an open source SW that manages VM on Kubernetes cluster uses
the mdev sysfs directory/file structure to discover mediated device in
nodes in the cluster.

v2:

- Fix the missing defination in gvt_type_attrs. (Zhenyu)

Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Hui Chun Ong <hui.chun.ong@intel.com>
Cc: Terrence Xu <terrence.xu@intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Signed-off-by: Zhi Wang <zhi.wang.linux@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220222150532.9090-1-zhi.a.wang@intel.com
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>