net:ethernet:aquantia: Workaround for HW checksum bug.

The hardware has the HW Checksum Offload bug when small
TCP patckets (with length <= 60 bytes) has wrong "checksum valid" bit.

The solution is - ignore checksum valid bit for small packets
(with length <= 60 bytes) and mark this as CHECKSUM_NONE to allow
network stack recalculate checksum itself.

Fixes: ccf9a5ed14be ("net: ethernet: aquantia: Atlantic A0 and B0 specific functions.")
Signed-off-by: Pavel Belous <Pavel.Belous@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>