irqchip/gic-v3: Fix refcount leak in gic_populate_ppi_partitions

of_find_node_by_phandle() returns a node pointer with refcount
incremented, we should use of_node_put() on it when not need anymore.
Add missing of_node_put() to avoid refcount leak.

Fixes: e3825ba1 ("irqchip/gic-v3: Add support for partitioned PPIs")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220601080930.31005-6-linmq006@gmail.com