spi: orion: Add of_node_put() before goto

Fix following coccicheck warning:
./drivers/spi/spi-orion.c:738:1-33: 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>
Link: https://lore.kernel.org/r/20211015034008.6357-1-wanjiabing@vivo.com
Signed-off-by: Mark Brown <broonie@kernel.org>