rpmsg: qcom_smd: Fix refcount leak in qcom_smd_parse_edge

of_parse_phandle() returns a node pointer with refcount
incremented, we should use of_node_put() on it when done.

Fixes: 53e2822e

 ("rpmsg: Introduce Qualcomm SMD backend")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220511120737.57374-1-linmq006@gmail.com