xfs: cleanup inode counter stats

xfs: cleanup inode counter stats

Most of them are unused, so mark them as such.  Give the remaining ones
names that match their use instead of the historic IRIX ones based on
vnodes.  Note that the names are purely internal to the XFS code, the
user interface is based on section names and arrays of counters.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>