powerpc/85xx: Make defconfigs consistent

The mpc85xx and corenet configs have many differences between them that
can't be explained by the target hardware of each config.  The next
patch will consolidate these targets using kconfig fragments; this
patch shows what the resulting defconfigs will look like (generated by
using savedefconfig on a fragment-generated config).

Signed-off-by: Scott Wood <scottwood@freescale.com>