e1000_null_write_reg
phy->ops.write_reg = e1000_null_write_reg;
phy->ops.write_reg_locked = e1000_null_write_reg;
phy->ops.write_reg_page = e1000_null_write_reg;
s32 e1000_null_write_reg(struct e1000_hw *hw, u32 offset, u16 data);