drm/i915: add VEBOX into debugfs

v2: Removed rebase relic VECS ring from i915_gem_request_info (Damien)

v3: s/hsw/hws in debugfs which I introduced in v2 (Jon)

Signed-off-by: Xiang, Haihao <haihao.xiang@intel.com>
[Order changed, and modified by]
CC:  "Bloomfield, Jon" <jon.bloomfield@intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>