drm/xe: Check result of drmm_mutex_init()

Although it's unlikely that drmm_mutex_init() will fail during
driver initialization, however we shouldn't ignore this case.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240409153132.1111-1-michal.wajdeczko@intel.com


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