net: phy: don't try to setup PHY-driven SFP cages when using genphy

In the Linux kernel, the following vulnerability has been resolved: net: phy: don't try to setup PHY-driven SFP cages when using genphy We don't have support for PHY-driver SFP cages with the genphy code. On top of that, it was found by sashiko that running sfp_bus_add_upstream() for genphy deadlocks, as for genphy the PHY probing runs under RTNL, which isn't the case for non-genphy drivers. This problem was reproduced, and does lead to a deadlock on RTNL. Before the blamed commit, the phy_sfp_probe() call was made by individual PHY drivers, so there was no way to get to the SFP probing path when using genphy. Let's therefore only run phy_sfp_probe when not using genphy.