net: mscc: ocelot: Add of_node_put() before goto

Fix following coccicheck warning:
./drivers/net/ethernet/mscc/ocelot_vsc7514.c:946:1-33: WARNING: Function
for_each_available_child_of_node should have of_node_put() before goto.

Early exits from for_each_available_child_of_node should decrement the
node reference counter.

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>