realtek: dsa: relax rtldsa_ethernet_loaded()

realtek: dsa: relax rtldsa_ethernet_loaded()

The Realtek DSA driver accesses the DTS at two locations.

- rtldsa_ethernet_loaded(): to check if ethernet driver is active
- rtl83xx_mdio_probe(): to create ports and link to pcs/phy

The first function does not directly search for the ethernet driver
but looks it up through the switch port nodes. Avoid future issues
and simply search all nodes that have a "ethernet" link to the
network driver.

While we are here add a missing put_device() to keep reference
counters clean.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/22235
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>