net: ethernet: ti: am65-cpsw: Call of_node_put() on error path

This code returns directly but it should instead call of_node_put()
to drop some reference counts.

Fixes: dab2b265

 ("net: ethernet: ti: am65-cpsw: Add support for SERDES configuration")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Link: https://lore.kernel.org/r/e3012f0c-1621-40e6-bf7d-03c276f6e07f@kili.mountain
Signed-off-by: Jakub Kicinski <kuba@kernel.org>