drm/xe: Stop ignoring errors from xe_ttm_sys_mgr_init()

xe_ttm_sys_mgr_init() already cleans up after itself, just return error
if that failed.

Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Reviewed-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250222001051.3012936-12-lucas.demarchi@intel.com


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