i2c: mux: gpio: Add missing fwnode_handle_put()

In i2c_mux_gpio_probe_fw(), we should add fwnode_handle_put()
when break out of the iteration device_for_each_child_node()
as it will automatically increase and decrease the refcounter.

Fixes: 98b2b712

 ("i2c: i2c-mux-gpio: Enable this driver in ACPI land")
Signed-off-by: Liang He <windhl@126.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>