net: aquantia: make symbol hw_atl_boards static

Fixes the following sparse warning:

drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c:50:34: warning:
 symbol 'hw_atl_boards' was not declared. Should it be static?

Fixes: 4948293f

 ("net: aquantia: Introduce new AQC devices and capabilities")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>