nvmet: propagate npwg topology

Ensure we propagate npwg to the target as well instead
of assuming its the same logical blocks per physical block.

This ensures devices with large IUs information properly
propagated on the target.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>