pmdomain: mediatek: fix use-after-free in scpsys_get_bus_protection_legacy()

In scpsys_get_bus_protection_legacy(), of_find_node_with_property()
returns a device node with its reference count incremented. The function
then calls of_node_put(node) before checking whether
syscon_regmap_lookup_by_phandle() returns an error. If an error occurs,
dev_err_probe() dereferences the node pointer to print diagnostic
information, but the node memory may have already been freed due to the
earlier of_node_put(), leading to a use-after-free vulnerability.

Fix this by moving the of_node_put() call after the error check, ensuring
the node is still valid when accessed in the error path.

Fixes: c29345fa5f66 ("pmdomain: mediatek: Refactor bus protection regmaps retrieval")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>