drm/xe/svm: fix dereferencing error pointer in drm_gpusvm_range_alloc()

xe_svm_range_alloc() returns ERR_PTR(-ENOMEM) on failure and there is a
dereference of "range" after that:

	-->     range->gpusvm = gpusvm;

In xe_svm_range_alloc(), when memory allocation fails return NULL
instead to handle this situation.

Fixes: 99624bd ("drm/gpusvm: Add support for GPU Shared Virtual Memory")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/adaef4dd-5866-48ca-bc22-4a1ddef20381@stanley.mountain/
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250323124907.3946370-1-harshit.m.mogalapalli@oracle.com
(cherry picked from commit 7a03221)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Author: harshimogalapalli

drivers/gpu/drm/xe/xe_svm.c

@@ -79,7 +79,7 @@ xe_svm_range_alloc(struct drm_gpusvm *gpusvm)
 
 	range = kzalloc(sizeof(*range), GFP_KERNEL);
 	if (!range)
-		return ERR_PTR(-ENOMEM);
+		return NULL;
 
 	INIT_LIST_HEAD(&range->garbage_collector_link);
 	xe_vm_get(gpusvm_to_vm(gpusvm));