net: thunder_bgx: add a missing of_node_put

[ Upstream commit 9d28f94912589f04ab51fbccaef287d4f40e0d1f ]

phy_np needs to get freed, just like the other child nodes.

Fixes: 5fc7cf17 ("net: thunderx: Cleanup PHY probing code.")
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250901213018.47392-1-rosenp@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>