nvme: factor out a nvme_configure_metadata helper

Factor out a helper from nvme_update_ns_info that configures the
per-namespaces metadata and PI settings.  Also make sure the helpers
clear the flags explicitly instead of all of ->features to allow for
potentially reusing ->features for future non-metadata flags.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>