Fix bhyve's NVMe Identify Namespace data

The NVMe Identify Namespace data structure's Number of LBA Formats
(NLBAF) field is a 0's based value (i.e. 0x0 means 1). Since the
emulation only supports a single format, set NLBAF to 0x0, not 1.

Reviewed by: imp, araujo, rgrimes
Approved by: imp (mentor)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D19579