nvme: check the PRINFO bit before deciding the host buffer length

According to NVMe spec v1.4, section 8.3.1, the PRINFO bit and
the metadata size play a vital role in deteriming the host buffer size.

If PRIFNO bit is set and MS==8, the host doesn't add the metadata buffer,
instead the controller adds it.

Signed-off-by: Revanth Rajashekar <revanth.rajashekar@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>