drm/i915: Move get-reset-stats ioctl from intel_uncore.c to i915_gem_context.c

The get-reset-stats ioctl reports upon the statistics (number of hangs,
be it as a victim or the guilty party) of a particular context. It is
semantically better as being part of i915_gem_context.c user interface,
as opposed to the hardware level access of intel_uncore.c

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463137042-9669-1-git-send-email-chris@chris-wilson.co.uk