net: phy: micrel_ksz90x1: switch to use ofnode apis

net: phy: micrel_ksz90x1: switch to use ofnode apis

phydev->node is phy node, phydev->dev->node is controller
and that current code is likely reading the properties from
controller node and not from phy. So, Use PHY API phy_get_ofnode()
helper to get PHY DT node and use ofnode_read_u32_default() to
read properties in phy node.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Changes for v2:
- Updated description
Signed-off-by: Michal Simek <michal.simek@xilinx.com>