phy: lynx-28g: implement phy_get_status() for CDR lock

commit  e0f3ef0b77ff1d7b858538cf444be020e40b04c7 from
https://github.com/nxp-imx/linux-imx

 lf-6.1.y

The MTIP backplane AN/LT block needs this extra information from the
SerDes PHY as another source of "link up" information.

Namely, at 25Gbps, the PCS does not have a MDIO_CTRL1_LPOWER bit
implemented in its MDIO_MMD_PCS:MDIO_CTRL1 register, so a phy_suspend()
procedure will not power down the link, and will not cause a link drop
event on the link partner.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>