[ARM] Orion: avoid setting ->force_phy_addr

The mv643xx_eth platform data field ->force_phy_addr only needs
to be set if the passed-in ->phy_addr field is zero (to distinguish
the case of not having specified a phy address
(force_phy_addr = 0) from the case where a phy address of zero needs
to be used (force_phy_addr = 1.))

Also, the ->force_phy_addr field will hopefully disappear in a
future mv643xx_eth reorganisation.

Therefore, this patch deletes the ->force_phy_addr field initialiser
from all Orion board code.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>