drm/xe/devcoredump: Remove IS_ERR_OR_NULL check for kzalloc

kzalloc returns a valid pointer or NULL if the allocation fails.
It never returns an error pointer. It is better to check for NULL directly.

Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250220001710.1803749-3-shuicheng.lin@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>