tile: avoid bug in tilepro net driver built with old hypervisor

Building against headers from an older Tilera hypervisor can cause
the frags[] array to be overrun.  Don't enable TSO in that case.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Signed-off-by: David S. Miller <davem@davemloft.net>