net: dsa: microchip: lan937x: fix reference count leak in lan937x_mdio_register()

This node pointer is returned by of_find_compatible_node() with
refcount incremented in this function. of_node_put() on it before
exitting this function.

Fixes: c9cd961c

 ("net: dsa: microchip: lan937x: add interrupt support for port phy link")
Signed-off-by: Sun Ke <sunke32@huawei.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20220908040226.871690-1-sunke32@huawei.com


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