net: mvmdio: disable/unprepare clocks in EPROBE_DEFER case

add appropriate calls to clk_disable_unprepare() by jumping to out_mdio
in case orion_mdio_probe() returns -EPROBE_DEFER.

Found by Linux Driver Verification project (linuxtesting.org).

Fixes: 3d604da1 ("net: mvmdio: get and enable optional clock")
Signed-off-by: Tobias Jordan <Tobias.Jordan@elektrobit.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>