soc: qcom: smp2p: Add of_node_put() before goto

Fix following coccicheck warning:
./drivers/soc/qcom/smp2p.c:501:1-33: WARNING: Function
for_each_available_child_of_node should have of_node_put() before goto

Early exits from for_each_available_child_of_node should decrement the
node reference counter.

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211014062350.8942-1-wanjiabing@vivo.com