drivers: net: phy: Ignore PHY ID 0 during PHY probing

Current code fails to probe some C45 PHYs that also respond to C22 reads.
This is the case for PHYs like Aquantia AQR112, Marvell 88X2242 (as
previously posted on the u-boot list).
If the PHY ID reads all 0s just ignore it and try the next devad.

Signed-off-by: Alex Marginean <alexm.osslist@gmail.com>
Reviewed-By: Ramon Fried <rfried.dev@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>