To count context losses, add struct i915_ctx_hang_stats for
both i915_hw_context and drm_i915_file_private.
drm_i915_file_private is used when there is no context.
v2: renamed and cleaned up the struct (Chris Wilson, Ian Romanick)
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Acked-by: Ben Widawsky <ben@bwidawsk.net> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>