drm/i915/rc6: throw out set() wrapper

Remove useless indirection that's just misdirection for the readers.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230421135948.2029121-1-jani.nikula@intel.com