powerpc: Remove CHRP and PMAC support from FSL defconfigs

Fix various defconfigs for Freescale chip based boards to remove
CONFIG_PPC_PMAC or CONFIG_PPC_CHRP which crept in due to those
being default y

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>