drm/i915/gt: move remaining debugfs interfaces into gt

The following interfaces:

  i915_wedged
  i915_forcewake_user

are dependent on gt values. Put them inside gt/ and drop the
"i915_" prefix name. This would be the new structure:

  dri/0/gt
  |
  +-- forcewake_user
  |
  \-- reset

For backwards compatibility with existing igt (and the slight
semantic difference between operating on the i915 abi entry
points and the deep gt info):

  dri/0
  |
  +-- i915_wedged
  |
  \-- i915_forcewake_user

remain at the top level.

Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211012221738.16029-1-andi@etezian.org