atlantic: remove architecture depends

This was tested on a RaptorCS Talos II with IBM POWER9 DD2.2 CPUs and an
ASUS XG-C100F PCI-e card without any issue. Speeds of ~8Gbps could be
attained with not-very-scientific (wget HTTP) both-ways measurements on
a local network. No warning or error reported in kernel logs. The
drivers seems to be portable enough for it not to be gated like such.

Signed-off-by: Léo Le Bouter <lle-bout@zaclys.net>
Signed-off-by: David S. Miller <davem@davemloft.net>