ar8216: Remove read/write/rmw member functions from ar8xxx_priv

ar8216: Remove read/write/rmw member functions from ar8xxx_priv

Remove read/write/rmw member functions from ar8xxx_priv

There seems to be no real benefit of the ar8xxx_priv member functions
read/write/rmw as one implementation exists for each of them only.
Especially ar8xxx_mii_rmw is assigned to priv->rmw first and then
mapped to ar8xxx_rmw.
Rename the ar8xxx_mii_.. functions to ar8xxx_.. and use them directly.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43742 3c298f89-4303-0410-b956-a3cf2f4a3e73