net: phy: Fix return value check phy_probe

Don't ignore return value of phy_probe() call as
the probe may fail and it needs to be reported.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>