net: ti: icssg_prueth: Fix NULL pointer dereference in prueth_probe()

In the Linux kernel, the following vulnerability has been resolved:

net: ti: icssg_prueth: Fix NULL pointer dereference in prueth_probe()

In the prueth_probe() function, if one of the calls to emac_phy_connect()

fails due to of_phy_connect() returning NULL, then the subsequent call to

phy_attached_info() will dereference a NULL pointer.

Check the return code of emac_phy_connect and fail cleanly if there is an

error.