drivers/net/macsonic.c: make functions static

This patch makes the following needlessly global functions static:
- macsonic_init()
- mac_onboard_sonic_ethernet_addr()
- mac_onboard_sonic_probe()
- mac_nubus_sonic_ethernet_addr()
- macsonic_ident()
- mac_nubus_sonic_probe()

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>