irqchip/realtek-rtl: Fix refcount leak in map_interrupts

of_find_node_by_phandle() returns a node pointer with refcount
incremented, we should use of_node_put() on it when not need anymore.
This function doesn't call of_node_put() in error path.
Call of_node_put() directly after of_property_read_u32() to cover
both normal path and error path.

Fixes: 9f3a0f34 ("irqchip: Add support for Realtek RTL838x/RTL839x interrupt controller")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220601080930.31005-7-linmq006@gmail.com