net: aquantia: fixed instack structure overflow

This is a real stack undercorruption found by kasan build.

The issue did no harm normally because it only overflowed
2 bytes after `bitary` array which on most architectures
were mapped into `err` local.

Fixes: bab6de8f

 ("net: ethernet: aquantia: Atlantic A0 and B0 specific functions.")
Signed-off-by: Nikita Danilov <nikita.danilov@aquantia.com>
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>