staging: octeon-ethernet: Move PHY activation to .ndo_open().

This prevents PHY not found types of errors for PHY drivers that are
probed after the Ethernet driver is probed, because the ifconfig UP is
done from userspace after all drivers have been probed.

Also avoid the cvmx-helper-board.c PHY code if a real PHY driver is
present, this allows a bootloader supplied device tree to specify the
PHY information rather than having to modify the code for each
different board.

Tested-by: Alex Smith <alex.smith@imgtec.com>
Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Alex Smith <alex.smith@imgtec.com>
Cc: devel@driverdev.osuosl.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>