net: aquantia: Convert hw and caps structures to const static pointers

This removes unnecessary structure copying, and prepares the driver for
separate firmware ops table introduction.

We also remove extra copy of capabilities structure (which is const actually)
and also replace it with a const pointer in aq_nic_cfg.

Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>