nvme: refactor nvme_validate_ns

Move the logic to revalidate the block_device size or remove the
namespace from the caller into nvme_validate_ns.  This removes
the return value and thus the status code translation.  Additionally
it also catches non-permanent errors from nvme_update_ns_info using
the existing logic.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>