net:ethernet:aquantia: Reset is_gso flag when EOP reached.

We need to reset is_gso flag when EOP reached (entire LSO packet processed).

Fixes: bab6de8f ("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>