ibm_newemac: Fix typo reading TAH channel info

This patch fixes a typo in ibm_newemac/core.c
(tah_port should be used instead of tah_ph)

Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>