nvme-cli: add endianess annotations

[Christoph Hellwig]

The intent of this series is to provide static type checking for the
little endian NVMe data structures using the sparse tool, similar to
the kernel.

To make my life easier I first converted nvme-cli to use a copy of
the kernel nvme.h header that defines the NVMe data structures.  The
next set of patches fixes various issues found by sparse as-is, followed
by adding support for checking the __le{16,32,64} annotations and using
the kernel cpu_to_le*/le*_to_cpu helpers, as well as fixing up various
missing endianess conversion uncovered by sparse.

To use sparse make sure both sparse and the cgcc wrapper are installed
and build nvme-cli using:

    make CC=cgcc

At least with my version of sparse there are a few warnings left that
aren't really nvme-clis faults during the build, and sparse will finally
crash after compiling nvme.c because it misparses the command line and
tries to interpret argconfig.o as a source file.  I'll plan to look into
that on the sparse side and hope to be able to provide a fix for that
issue to the sparse maintainers.