generic: ar8216: reuse the private data from ar8216_probe

The private data of the switch is already
allocated in ar8216_priv, assign that to
each PHY on the same MDIO bus. Also remove
the redundant code from ar8216_config_init.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 35559