pinctrl: devicetree: fix refcount leak in pinctrl_dt_to_map()

In the Linux kernel, the following vulnerability has been resolved: pinctrl: devicetree: fix refcount leak in pinctrl_dt_to_map() If we fail to allocate propname buffer, we need to drop the reference count we just took. Because the pinctrl_dt_free_maps() includes the droping operation, here we call it directly.