net: ethernet: arc: Fix a potential memory leak if an optional regulator is deferred

If the optional regulator is deferred, we must release some resources.
They will be re-allocated when the probe function will be called again.

Fixes: 6eacf311 ("ethernet: arc: Add support for Rockchip SoC layer device tree bindings")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>