drm/xe: Remove uninitialized variable from warning

drm/xe: Remove uninitialized variable from warning

"err" is not initialized when failing to create and add the freq0 sysfs
file. Remove it from the message. This fixes the following warning with
clang:

	../drivers/gpu/drm/xe/xe_gt_freq.c:202:30: error: variable 'err' is uninitialized when used here [-Werror,-Wuninitialized]
				 kobject_name(gt->sysfs), err);
							  ^~~

Fixes: bef52b5c7a19 ("drm/xe: Create a xe_gt_freq component for raw management and sysfs")
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://lore.kernel.org/r/20231220161923.3740489-1-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>