net:ethernet:aquantia: Fix for incorrect speed index.

The driver choose the optimal interrupt throttling settings depends
of current link speed.
Due this bug link_status field from aq_hw is never updated and as result
always used same interrupt throttling values.

Fixes: 3d2ff7eebe26 ("net: ethernet: aquantia: Atlantic hardware abstraction layer")
Signed-off-by: Pavel Belous <Pavel.Belous@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>