drm/i915: Remove debugfs i915_drpc_info and i915_forcewake_domains

The two files have been duplicated under the gt/ subdir and since there
are not apparent users looking for them at the old location lets simply
remove them and duplicated code.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Andi Shyti <andi.shyti@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200310164733.26487-1-tvrtko.ursulin@linux.intel.com