nvme: modify flbas rsvd bits to be used

nvme: modify flbas rsvd bits to be used

flbas Bits 6:5 indicate the most significant 2 bits of
the Format Index of the supported LBA Format indicated
in this data structure that was used to format the namespace

using libnvme util function nvme_id_ns_flbas_to_lbaf_inuse
to extract currently used lba index

Signed-off-by: Steven Seungcheol Lee <sc108.lee@samsung.com>