Add a new flag to mark memory region that are used as non-volatile, by
NVDIMM for example. That bit is propagated down to the flat view, and
reflected in HMP info mtree with a "nv-" prefix on the memory type.

This way, guest_phys_blocks_region_add() can skip the NV memory
regions for dumps and TCG memory clear in a following patch.

Cc: dgilbert@redhat.com
Cc: imammedo@redhat.com
Cc: pbonzini@redhat.com
Cc: guangrong.xiao@linux.intel.com
Cc: mst@redhat.com
Cc: xiaoguangrong.eric@gmail.com
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20181003114454.5662-2-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>