drm/i915/debugfs: move uC printers and update debugfs file names

Move the printers to the respective files for clarity. The
guc_load_status debugfs has been squashed in the guc_info one, has
having separate ones wasn't very useful. The HuC debugfs has been
renamed huc_info to match.

v2: keep printing HUC_STATUS2 (Tony), avoid const->non-const
    container_of (Jani)

Suggested-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Tony Ye <tony.ye@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200326181121.16869-5-daniele.ceraolospurio@intel.com