drm/i915: remove unused leftover basedie step code

drm/i915: remove unused leftover basedie step code

The basedie step initialization as well as its last users were removed
in commit 326e30e4624c ("drm/i915: Drop dead code for pvc"). Follow
through with removing the unused macros and struct member and debug
logging.

Suggested-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240822143946.2526425-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>