net/sunbmac.c section fix

This patch fixes the following section mismatch:

<--  snip  -->

...
WARNING: drivers/net/sunbmac.o(.devinit.text+0x24): Section mismatch in reference from the function bigmac_sbus_probe() to the function .init.text:bigmac_ether_init()
...

<--  snip  -->

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>