drm/xe: Remove unused code in devcoredump_snapshot()

The deleted code is no longer needed because patch "drm/xe/guc: Plumb
GuC-capture into dev coredump" has removed the related usage code.
Remove the code to tidy up the function.

v2: s/bacause/because

Reviewed-by: Zhanjun Dong <zhanjun.dong@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250707004911.3502904-5-shuicheng.lin@intel.com