net: pcs: Add missing put_device call in miic_create

The reference of pdev->dev is taken by of_find_device_by_node, so
it should be released when not need anymore.

Fixes: 7dc54d3b

 ("net: pcs: add Renesas MII converter driver")
Signed-off-by: Xiang Yang <xiangyang3@huawei.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>