igc_null_read_reg
phy->ops.read_reg = igc_null_read_reg;
phy->ops.read_reg_locked = igc_null_read_reg;
phy->ops.read_reg_page = igc_null_read_reg;
s32 igc_null_read_reg(struct igc_hw *hw, u32 offset, u16 *data);