ibm_newemac: Fix section mismatch warnings

This patch fixes several section mismatch warnings in the
ibm_newemac driver similar to:

WARNING: vmlinux.o(.devinit.text+0x3a04): Section mismatch in reference from the function emac_probe() to the function .devexit.text:tah_detach()
The function __devinit emac_probe() references
a function __devexit tah_detach().

Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>