If mv643xx_eth_shared_of_probe() fails, mv643xx_eth_shared_probe()
leaves clk enabled.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: NAlexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>