[MTD] remove code associated with !CONFIG_PPC_MERGE

Now that arch/ppc is gone we don't need CONFIG_PPC_MERGE anymore
remove the dead code associated with !CONFIG_PPC_MERGE.

The mtd maps should be using the OF based mechanism.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>