Revert changes to shared code of the ixl and ixlv drivers to allow
for easier long-term maintainability.

Restrict the drivers to building on amd64 for now as it is
only tested on that 64bit architecture.

Just depend on PCI and neither INET nor INET6; also make sure we
can build individual drivers and they do not depend on each other
anymore.

Reviewed by:	gnn, eric.joyner intel.com