net: ethernet: arc: add the missed clk_disable_unprepare

[ Upstream commit 4202e219edd6cc164c042e16fa327525410705ae ]

The remove misses to disable and unprepare priv->macclk like what is done
when probe fails.
Add the missed call in remove.

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>