System hang via recursive pinctrl mutex acquisition

Improper locking in the Linux kernel pinctrl core allows local users to hang the system during deferred device-probe handling. create_pinctrl() holds pinctrl_maps_mutex when add_setting() returns -EPROBE_DEFER, then calls pinctrl_free(), which tries to acquire the same mutex and deadlocks. Exploitation requires local low-privileged access and execution of the affected deferred-probe path; the documented consequence is loss of system availability.