net: mdiobus: release reset_gpio in mdiobus_unregister_device()

net: mdiobus: release reset_gpio in mdiobus_unregister_device()

reset_gpio is claimed in mdiobus_register_device(), but it is not
released in mdiobus_unregister_device(). It is instead only
released when the whole MDIO bus is unregistered.
When a device uses the reset_gpio property, it becomes impossible
to unregister it and register it again, because the GPIO remains
claimed.
This patch resolves that issue.

Fixes: bafbdd527d56 ("phylib: Add device reset GPIO support") # see notes
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Cc: Csókás Bence <csokas.bence@prolan.hu>
[ csokas.bence: Resolve rebase conflict and clarify msg ]
Signed-off-by: Buday Csaba <buday.csaba@prolan.hu>
Link: https://patch.msgid.link/20250807135449.254254-2-csokas.bence@prolan.hu
Signed-off-by: Paolo Abeni <pabeni@redhat.com>