powerpc: Remove duplicate cacheable_memcpy/memzero functions

These functions are only used from one place each.  If the cacheable_*
versions really are more efficient, then those changes should be
migrated into the common code instead.

NOTE: The old routines are just flat buggy on kernels that support
      hardware with different cacheline sizes.

Signed-off-by: Kyle Moffett <Kyle.D.Moffett@boeing.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>