net: dsa: rzn1-a5psw: add missing of_node_put() in a5psw_pcs_get()

of_parse_phandle() will increase the refcount of 'pcs_node', so add
of_node_put() before return from a5psw_pcs_get().

Fixes: 888cdb89

 ("net: dsa: rzn1-a5psw: add Renesas RZ/N1 advanced 5 port switch driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220630014153.1888811-1-yangyingliang@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>