thermal/drivers/sprd: Add missing of_node_put for loop iteration

Early exits from for_each_available_child_of_node() should decrement the
node reference counter.  Reported by Coccinelle:

  drivers/thermal/sprd_thermal.c:387:1-23: WARNING:
    Function "for_each_child_of_node" should have of_node_put() before goto around lines 391.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Chunyan Zhang <zhang.lyra@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210614192230.19248-2-krzysztof.kozlowski@canonical.com