if of_find_device_by_node() succeed, pinctrl_falcon_probe() doesn't have
a corresponding put_device(). Thus add put_device() to fix the exception
handling for this function implementation.

Fixes: e316cb2b ("OF: pinctrl: MIPS: lantiq: adds support for FALCON SoC")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20201119011219.2248232-1-yukuai3@huawei.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>