net: emacps: Remove dead code in xemacps_probe()

xemacps_mii_probe() always returns 0 or -1, so the condition rc == -2
in xemacps_probe() will never hold true.

Also, we should not unregister and free lp->mii_bus in xemacps_probe()
anyway, as this is the job of xemacps_remove().

Signed-off-by: Thomas Betker <thomas.betker@rohde-schwarz.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>