powerpc/hotplug-mem: Fix missing endian conversion of aa_index

commit dc421b200f91930c9c6a9586810ff8c232cf10fc upstream.

When adding or removing memory, the aa_index (affinity value) for the
memblock must also be converted to match the endianness of the rest
of the 'ibm,dynamic-memory' property.  Otherwise, subsequent retrieval
of the attribute will likely lead to non-existent nodes, followed by
using the default node in the code inappropriately.

Fixes: 5f97b2a0 ("powerpc/pseries: Implement memory hotplug add in the kernel")
Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>