eal/linux: restore specific hugepage ordering for ppc

eal/linux: restore specific hugepage ordering for ppc

An ifdef present in eal_memory.c references "RTE_ARCH_PPC64" when
it should actually use "RTE_ARCH_PPC_64".  Simple testing revealed
that both the PPC_64 and non-PPC_64 versions of the code involved
work, but the PPC_64 version of the code is retained to be
consistent with other instances in the same file where mmapped
memory is accessed in reverse order on Power platforms.

Fixes: 66cc45e293ed ("mem: replace memseg with memseg lists")
Cc: stable@dpdk.org
Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>