drivers: explicit initialization of pci drivers

drivers: explicit initialization of pci drivers

Upcoming drivers will need to be able to support other bus types.
This is a transparent change to how struct eth_driver is initialized.
It has not function or ABI layout impact, but makes adding a later
bus type (Xen, Hyper-V, ...) much easier.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>