powerpc/8xx: Add missing of_node_put() in tqm8xx_setup.c

In init_ioports(), of_find_node_by_name() will return a node pointer
with refcount incremented. The reference should be dropped with
of_node_put() when it is not used anymore.

Signed-off-by: Liang He <windhl@126.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220618024930.4056825-1-windhl@126.com