drm/xe/lrc: Reduce scope of empty lrc data

drm/xe/lrc: Reduce scope of empty lrc data

The only case in which new lrc data is created from scratch is when it's
called prior to recording the default lrc. There's no need to check for
NULL init_data since in that case the function already failed: just move
the allocation where it's needed.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250710-lrc-refactors-v2-1-a5e2ca03f6bd@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>