net/phy: Fix PHY id for VSC8514

In the current Datasheet for VSC8514 there is a mistake, saying that
the PHY id is 0x70570. The real value in the identifier registers is
0x70670. Linux PHY driver uses 0x70670 also.

Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@freescale.com>
Cc: York Sun <yorksun@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>