ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

On reboot, all memory that was previously added using object_add and
device_add is placed in this DIMM area.

The new SPAPR_LMB_FLAGS_HOTREMOVABLE flag helps Linux to put this memory in
the correct memory zone, so no unmovable allocations are made there,
allowing the object to be easily hot-removed by device_del and
object_del.

This new flag was accepted in Power Architecture documentation.

Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
Reviewed-by: Bharata B Rao <bharata@linux.ibm.com>
Message-Id: <20200511200201.58537-1-leobras.c@gmail.com>
[dwg: Fixed syntax error spotted by Cédric Le Goater]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>