bfin_mac: fix build error due to net_device_ops convert

The previous commit "convert to net_device_ops" broke the Blackfin MAC
driver as it declared the new structure before the function it used:
  CC      drivers/net/bfin_mac.o
drivers/net/bfin_mac.c:984: error: ‘bfin_mac_close’ undeclared here (not in a function)
make[1]: *** [drivers/net/bfin_mac.o] Error 1

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David S. Miller <davem@davemloft.net>