block/nvme: support larger that 512 bytes sector devices

Currently the driver hardcodes the sector size to 512,
and doesn't check the underlying device. Fix that.

Also fail if underlying nvme device is formatted with metadata
as this needs special support.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-id: 20190716163020.13383-3-mlevitsk@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>