treewide: use dm_mdio_read/write/reset() wrappers

Use the new dm_mdio_read/write/reset() wrappers treewide, instead of
always getting and dereferencing MDIO operations structure pointer.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>